diff --git a/build_packages b/build_packages
index a103c31..bc9523a 100755
--- a/build_packages
+++ b/build_packages
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Copyright 2022 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -9,529 +9,15 @@
 # Script must run inside the chroot
 restart_in_chroot_if_needed "$@"
 
-assert_not_root_user
+new_script="build_packages"
+cat <<EOF
+$0: This script is deprecated and will be removed.
+All users must migrate to ${new_script} in chromite/bin.
+You can simply change all references of $0 to \`${new_script}\`
+from \$PATH (in chromite/bin/).
+This old script will be removed by July 2022.
+If you have questions or found code that needs updating, please contact
+chromium-os-dev@, or file a bug at go/cros-build-bug.
+EOF
+exec "${CHROMITE_BIN}/${new_script}" "$@"
 
-# Developer-visible flags.
-DEFINE_string board "${DEFAULT_BOARD}" \
-  "The board to build packages for."
-DEFINE_boolean usepkg "${FLAGS_TRUE}" \
-  "Use binary packages to bootstrap when possible."
-DEFINE_boolean usepkgonly "${FLAGS_FALSE}" \
-  "Only use binary packages to bootstrap; abort if any are missing."
-DEFINE_boolean workon "${FLAGS_TRUE}" \
-  "Force-build workon packages."
-DEFINE_boolean showoutput "${FLAGS_FALSE}" \
-  "Show all output from parallel_emerge."
-DEFINE_boolean withautotest "${FLAGS_TRUE}" \
-  "Build autotest client code."
-DEFINE_boolean withdebugsymbols "${FLAGS_FALSE}" \
-  "Install the debug symbols for all packages"
-DEFINE_boolean withrevdeps "${FLAGS_TRUE}" \
-  "Calculate reverse dependencies on changed ebuilds."
-DEFINE_boolean autosetgov "${FLAGS_FALSE}" \
-  "Automatically set cpu governor to 'performance'."
-DEFINE_boolean autosetgov_sticky "${FLAGS_FALSE}" \
-  "Remember --autosetgov setting for future runs."
-DEFINE_boolean use_any_chrome "${FLAGS_TRUE}" \
-  "Use any Chrome prebuilt available, even if the prebuilt doesn't match exactly."
-DEFINE_boolean cleanbuild "${FLAGS_FALSE}" \
-  "Perform a clean build; delete sysroot if it exists before building."
-DEFINE_boolean internal "${FLAGS_FALSE}" \
-  "Build the internal version of chrome (set the chrome_internal USE flag)."
-DEFINE_boolean pretend "${FLAGS_FALSE}" \
-  "Don't build packages, just display which packages would have been installed."
-
-# The --board_root flag specifies the environment variables ROOT and PKGDIR.
-# This allows fetching and emerging of all packages to specified board_root.
-# Note that --board_root will setup the board normally in /build/$BOARD, if it's
-# not setup yet. It also expects the toolchain to already be installed in the
-# board_root. --usepkgonly and --norebuild are required, because building is not
-# supported when board_root is set.
-# enforce this)."
-DEFINE_string board_root "" \
-  "Emerge packages to board_root."
-
-FLAGS_HELP="usage: $(basename $0) [flags] [packages]
-
-build_packages updates the set of binary packages needed by Chrome OS. It will
-cross compile all packages that have been updated into the given target's root
-and build binary packages as a side-effect. The output packages will be picked
-up by the build_image script to put together a bootable Chrome OS image.
-
-If [packages] are specified, only build those specific packages (and any
-dependencies they might need).
-
-For the fastest builds, use --nowithautotest --noworkon.
-"
-
-# The following options are advanced options, only available to those willing
-# to read the source code. They are not shown in help output, since they are
-# not needed for the typical developer workflow.
-DEFINE_string accept_licenses "" \
-  "Licenses to append to the accept list."
-DEFINE_boolean eclean "${FLAGS_TRUE}" \
-  "Run eclean to delete old binpkgs."
-DEFINE_integer jobs -1 \
-  "How many packages to build in parallel at maximum."
-DEFINE_boolean norebuild "${FLAGS_FALSE}" \
-  "Don't automatically rebuild dependencies."
-DEFINE_boolean skip_chroot_upgrade "${FLAGS_FALSE}" \
-  "Don't run the chroot upgrade automatically; use with care."
-DEFINE_boolean skip_setup_board "${FLAGS_FALSE}" \
-  "Don't run setup_board. Implies skip_chroot_upgrade and" \
-  "skip_toolchain_update."
-DEFINE_boolean skip_toolchain_update "${FLAGS_FALSE}" \
-  "Don't update toolchain automatically."
-DEFINE_boolean withdev "${FLAGS_TRUE}" \
-  "Build useful developer friendly utilities."
-DEFINE_boolean withdebug "${FLAGS_TRUE}" \
-  "Build debug versions of Chromium-OS-specific packages."
-DEFINE_boolean withfactory "${FLAGS_TRUE}" \
-  "Build factory installer."
-DEFINE_boolean withtest "${FLAGS_TRUE}" \
-  "Build packages required for testing."
-DEFINE_boolean expandedbinhosts "${FLAGS_TRUE}" \
-  "Allow expanded binhost inheritance."
-
-# The --reuse_pkgs_from_local_boards flag tells Portage to share binary
-# packages between boards that are built locally, so that the total time
-# required to build several boards is reduced. This flag is only useful
-# when you are not able to use remote binary packages, since remote binary
-# packages are usually more up to date than anything you have locally.
-DEFINE_boolean reuse_pkgs_from_local_boards "${FLAGS_FALSE}" \
-  "Bootstrap from local packages instead of remote packages."
-
-# --run_goma option is designed to be used on bots.
-# If you're trying to build pacakges with goma in your local dev env, this is
-# *not* the option you're looking for. Please see comments below.
-# This option; 1) starts goma, 2) builds packages (expecting that goma is
-# used), then 3) stops goma explicitly.
-# 3) is a request from the goma team, so that stats/logs can be taken.
-# Note: GOMA_DIR and GOMA_SERVICE_ACCOUNT_JSON_FILE are expected to be passed
-# via env var.
-#
-# In local dev env cases, compiler_proxy is expected to keep running.
-# In such a case;
-#   $ python ${GOMA_DIR}/goma_ctl.py ensure_start
-#   $ ./build_packages (... and options without --run_goma ...)
-# is an expected commandline sequence. If you set --run_goma flag while
-# compiler_proxy is already running, the existing compiler_proxy will be
-# stopped.
-DEFINE_boolean run_goma "${FLAGS_FALSE}" \
-  "If set to true, (re)starts goma, builds packages, and then stops goma."
-
-# This option is for building chrome remotely.
-#1) starts reproxy 2) builds chrome with reproxy and 3) stops reproxy so
-# logs/stats can be collected.
-# Note: RECLIENT_DIR and REPROXY_CFG are expected to be passed via env var.
-DEFINE_boolean run_remoteexec "${FLAGS_FALSE}" \
-  "If set to true, starts RBE reproxy, builds packages, and then stops reproxy."
-
-# Parse command line
-FLAGS "$@" || exit 1
-eval set -- "${FLAGS_ARGV}"
-
-# Die on any errors.
-switch_to_strict_mode
-
-# Chrome packages that need to be treated the same. These are the chrome and
-# chrome follow-on packages that share the same version as chrome and are
-# updated in lock step.
-CHROME_PACKAGES=(
-  "chromeos-base/chromeos-chrome"
-  "chromeos-base/chrome-icu"
-)
-
-if [[ "${FLAGS_internal}" -eq "${FLAGS_TRUE}" ]]; then
-  export USE="${USE} chrome_internal"
-fi
-
-# Right now build_packages has to be run from scripts/
-. ${SRC_ROOT}/third_party/chromiumos-overlay/chromeos/config/chromeos_version.sh
-
-# On some systems, powersave can take a long time to ramp up.  Inform the user
-# so they can get faster builds.  https://crbug.com/1008932
-CHROMITE_CONFIG_DIR=$(
-  python -c 'from chromite.lib.chromite_config import DIR; print(DIR)')
-CONFIG_AUTOSETGOV="${CHROMITE_CONFIG_DIR}/autosetgov"
-if [[ "${FLAGS_autosetgov_sticky}" -eq "${FLAGS_TRUE}" ]]; then
-  mkdir -p "${CHROMITE_CONFIG_DIR}"
-  if [[ "${FLAGS_autosetgov}" -eq "${FLAGS_TRUE}" ]]; then
-    info "Future runs of build_packages will *always* use --autosetgov"
-    echo "# Delete this file to turn off automatic build_packages" \
-      "--autosetgov." >"${CONFIG_AUTOSETGOV}"
-  else
-    info "Future runs of build_packages will respect --autosetgov"
-    rm -f "${CONFIG_AUTOSETGOV}"
-  fi
-fi
-if [[ -e "${CONFIG_AUTOSETGOV}" ]]; then
-  FLAGS_autosetgov="${FLAGS_TRUE}"
-fi
-# Make sure we can actually support "performance".
-if grep -qs performance \
-     /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors; then
-  curr_gov=$(sort -u /sys/devices/system/cpu/cpufreq/policy*/scaling_governor)
-  if [[ "${curr_gov}" != "performance" ]]; then
-    if [[ "${FLAGS_autosetgov}" -eq "${FLAGS_TRUE}" ]]; then
-      if [[ $(echo "${curr_gov}" | wc -l) -gt 1 ]]; then
-        warn "Too many active CPU governors; refusing to use 'performance'."
-      else
-        info "Temporarily setting cpu governor to 'performance'"
-        trap "sudo cpupower -c all frequency-set -g powersave >&/dev/null" EXIT
-        sudo cpupower -c all frequency-set -g performance >&/dev/null
-      fi
-    elif [[ "${curr_gov}" == "powersave" ]]; then
-      warn "Current CPU governor set to 'powersave' which can slow down builds."
-      warn "Use --autosetgov to automatically (and temporarily) switch to" \
-        "'performance'."
-    fi
-  fi
-fi
-
-if [[ -z "${FLAGS_board}" ]]; then
-  echo "Error: --board is required."
-  exit 1
-fi
-
-BOARD_ROOT="${FLAGS_board_root:-/build/${FLAGS_board}}"
-
-# Skip revdeps when we don't already have a built sysroot.
-if [[ "${FLAGS_cleanbuild}" -eq "${FLAGS_TRUE}" || ! -d "${BOARD_ROOT}" ]]; then
-  SKIP_REVDEPS="${FLAGS_TRUE}"
-else
-  SKIP_REVDEPS="${FLAGS_FALSE}"
-fi
-
-if [[ "${FLAGS_skip_setup_board}" -eq "${FLAGS_FALSE}" ]]; then
-  # Before we can run any tools, we need to update chroot or setup_board.
-  UPDATE_ARGS=()
-  if [[ -n ${FLAGS_accept_licenses} ]]; then
-    UPDATE_ARGS+=( --accept-licenses "${FLAGS_accept_licenses}" )
-  fi
-  if [ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ]; then
-    UPDATE_ARGS+=( --usepkg )
-  else
-    UPDATE_ARGS+=( --nousepkg )
-  fi
-  if [[ "${FLAGS_jobs}" -ne -1 ]]; then
-    UPDATE_ARGS+=( --jobs=${FLAGS_jobs} )
-  fi
-  if [ "${FLAGS_reuse_pkgs_from_local_boards}" -eq "${FLAGS_TRUE}" ]; then
-    UPDATE_ARGS+=( --reuse-pkgs-from-local-boards )
-  fi
-  if [ "${FLAGS_skip_toolchain_update}" -eq "${FLAGS_TRUE}" ]; then
-    UPDATE_ARGS+=( --skip-toolchain-update )
-  fi
-  if [ "${FLAGS_skip_chroot_upgrade}" -eq "${FLAGS_TRUE}" ]; then
-    UPDATE_ARGS+=( --skip-chroot-upgrade )
-  fi
-  if [[ -n ${FLAGS_board_root} ]]; then
-    UPDATE_ARGS+=( --board-root "${FLAGS_board_root}" )
-  fi
-  if [ "${FLAGS_cleanbuild}" -eq "${FLAGS_TRUE}" ]; then
-    UPDATE_ARGS+=( --force )
-  fi
-  if [[ "${FLAGS_expandedbinhosts}" -eq "${FLAGS_FALSE}" ]]; then
-    UPDATE_ARGS+=( --fewer-binhosts )
-  fi
-
-  setup_board --quiet --board=${FLAGS_board} "${UPDATE_ARGS[@]}"
-fi
-
-sudo_clear_shadow_locks "${BOARD_ROOT}"
-PORTAGE_BINHOST=$(portageq-${FLAGS_board} envvar 'PORTAGE_BINHOST')
-info "PORTAGE_BINHOST: ${PORTAGE_BINHOST}"
-
-
-# Setup all the emerge command/flags.
-EMERGE_FLAGS=( -uDNv --backtrack=30 --newrepo --with-test-deps y )
-
-EMERGE_CMD=(
-  "${CHROMITE_BIN}/parallel_emerge"
-  --board=${FLAGS_board}
-)
-
-if [[ "${FLAGS_use_any_chrome}" -eq "${FLAGS_TRUE}" ]]; then
-  for pkg in "${CHROME_PACKAGES[@]}"; do
-    EMERGE_CMD+=( "--force-remote-binary=${pkg}" )
-  done
-fi
-
-EMERGE_CMD+=( ${EXTRA_BOARD_FLAGS} )
-
-if [[ "${FLAGS_pretend}" -eq "${FLAGS_TRUE}" ]]; then
-  EMERGE_FLAGS+=( "--pretend" )
-fi
-
-if [[ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ||
-      "${FLAGS_reuse_pkgs_from_local_boards}" -eq "${FLAGS_TRUE}" ||
-      "${FLAGS_usepkgonly}" -eq "${FLAGS_TRUE}" ]]; then
-  # Use binary packages. Include all build-time dependencies,
-  # so as to avoid unnecessary differences between source
-  # and binary builds.
-  EMERGE_FLAGS+=( --getbinpkg --with-bdeps y )
-  if [[ ${FLAGS_usepkgonly} -eq ${FLAGS_TRUE} ]]; then
-    EMERGE_FLAGS+=( --usepkgonly )
-  else
-    EMERGE_FLAGS+=( --usepkg )
-  fi
-fi
-
-if [[ "${FLAGS_jobs}" -ne -1 ]]; then
-  EMERGE_FLAGS+=( --jobs=${FLAGS_jobs} )
-fi
-
-if [[ "${FLAGS_norebuild}" -eq "${FLAGS_FALSE}" ]]; then
-  EMERGE_FLAGS+=( --rebuild-if-new-rev )
-fi
-if [[ "${FLAGS_showoutput}" -eq "${FLAGS_TRUE}" ]]; then
-  EMERGE_FLAGS+=( --show-output )
-fi
-
-if [[ "${FLAGS_withdebug}" -eq "${FLAGS_FALSE}" ]]; then
-  export USE="${USE} -cros-debug"
-fi
-
-# Figure out which packages we should be building.
-PACKAGES=( "$@" )
-FORCE_LOCAL_BUILD_PKGS=()
-if [[ $# -eq 0 ]]; then
-  PACKAGES=( virtual/target-os )
-  if [[ "${FLAGS_withdev}" -eq "${FLAGS_TRUE}" ]]; then
-    PACKAGES+=( virtual/target-os-dev )
-  fi
-  if [[ "${FLAGS_withfactory}" -eq "${FLAGS_TRUE}" ]]; then
-    PACKAGES+=( virtual/target-os-factory )
-    PACKAGES+=( virtual/target-os-factory-shim )
-  fi
-  if [[ "${FLAGS_withtest}" -eq "${FLAGS_TRUE}" ]]; then
-    PACKAGES+=( virtual/target-os-test )
-    # chromeos-ssh-testkeys may generate ssh keys if the right USE flag is set.
-    # We force rebuilding this package from source every time, so that
-    # consecutive builds don't share ssh keys.
-    FORCE_LOCAL_BUILD_PKGS+=( chromeos-base/chromeos-ssh-testkeys )
-  fi
-  if [[ "${FLAGS_withautotest}" -eq "${FLAGS_TRUE}" ]]; then
-    PACKAGES+=( chromeos-base/autotest-all )
-  fi
-fi
-
-info "Rebuilding Portage cache"
-# Before running any emerge operations, regenerate the Portage dependency cache
-# in parallel.
-info_run "${EMERGE_CMD[@]}" --regen --quiet
-
-# Clean out any stale binpkgs we've accumulated. This is done immediately after
-# regenerating the cache in case ebuilds have been removed (e.g. from a revert).
-if [[ "${FLAGS_eclean}" -eq "${FLAGS_TRUE}" ]]; then
-  info "Cleaning stale binpkgs"
-  get_eclean_exclusions | "eclean-${FLAGS_board}" -e /dev/stdin packages
-fi
-
-# Verify that all packages can be emerged from scratch, without any
-# backtracking. Only print the output if this step fails.
-info "Checking package dependencies are correct: ${PACKAGES[*]}"
-if ! OUTPUT=$(emerge-${FLAGS_board} -pe --backtrack=0 \
-              "${PACKAGES[@]}" 2>&1); then
-  printf "%s\n" "${OUTPUT}"
-  die_notrace "emerge detected broken ebuilds. See error message above."
-fi
-
-# Build cros_workon packages when they are changed.
-CROS_WORKON_PKGS=()
-if [ "${FLAGS_workon}" -eq "${FLAGS_TRUE}" ]; then
-  LIST_MODIFIED_PACKAGES="${CHROMITE_BIN}/cros_list_modified_packages"
-  MODIFIED_PACKAGES=( $("${LIST_MODIFIED_PACKAGES}" --board=${FLAGS_board}) )
-  info "cros_workon modified packages '${MODIFIED_PACKAGES[*]}' detected"
-  CROS_WORKON_PKGS+=( "${MODIFIED_PACKAGES[@]}" )
-
-  # TODO(anush): Make chrome a fake cros-workon package.
-  if [[ -n "${CHROME_ORIGIN}" ]]; then
-    CROS_WORKON_PKGS+=( "${CHROME_PACKAGES[@]}" )
-  fi
-fi
-
-# cros_workon packages always have to be rebuilt.
-FORCE_LOCAL_BUILD_PKGS+=( "${CROS_WORKON_PKGS[@]}" )
-
-# Any package that directly depends on an active cros_workon package also needs
-# to be rebuilt in order to be correctly built against the current set of
-# changes a user may have made to the cros_workon package.
-if [[ ${#CROS_WORKON_PKGS[@]} -gt 0 ]]; then
-  # Collect all installed packages that depend on active cros_workon packages.
-  WORKON_PKG_CONSUMERS=()
-  mapfile -t WORKON_PKG_CONSUMERS < <( \
-    equery-${FLAGS_board} -q depends "${CROS_WORKON_PKGS[@]}" | \
-    sort -u | \
-    grep -Ev "^\s*$" )
-
-  # Transform this list of packages with versions in to a list of just
-  # $CATEGORY/$NAME entries, since we don't want to pass packages with explicit
-  # version numbers as arguments to `emerge`.
-  if [[ ${#WORKON_PKG_CONSUMERS[@]} -gt 0 ]]; then
-    WORKON_REBUILD_PKGS=()
-    mapfile -t WORKON_REBUILD_PKGS < <( \
-      equery-${FLAGS_board} list -p -o --format='$category/$name' \
-        "${WORKON_PKG_CONSUMERS[@]}" | sort -u )
-
-    info "The following packages depend directly on an active" \
-      "cros_workon package and will be rebuilt: ${WORKON_REBUILD_PKGS[*]}"
-
-    FORCE_LOCAL_BUILD_PKGS+=( "${WORKON_REBUILD_PKGS[@]}" )
-  fi
-fi
-
-if [[ -n "${FLAGS_board_root}" ]]; then
-  export ROOT="${FLAGS_board_root}"
-  export PORTAGE_CONFIGROOT="${ROOT}"
-  export SYSROOT="${ROOT}"
-  export PKGDIR="${ROOT}"/packages
-fi
-
-# Temporarily modify the emerge flags so we can calculate the revdeps
-# on the modified packages.
-if [[ "${FLAGS_withrevdeps}" -eq "${FLAGS_TRUE}" &&
-      "${SKIP_REVDEPS}" -eq "${FLAGS_FALSE}" ]]; then
-  info "starting reverse dependency calculations ..."
-  SIM_EMERGE_FLAGS=( "${EMERGE_FLAGS[@]}" --pretend --columns )
-
-  if [[ ${#PACKAGES[@]} -gt 0 ]]; then
-    SIM_EMERGE_FLAGS+=(
-      --reinstall-atoms="${PACKAGES[*]}"
-      --usepkg-exclude="${PACKAGES[*]}"
-    )
-  fi
-
-  # cros-workon packages are always going to be force reinstalled, so we add
-  # the forced reinstall behavior to the modified package calculation. This is
-  # necessary to include when a user has already installed a 9999 ebuild and is
-  # now reinstalling that package with additional local changes, because
-  # otherwise the modified package calculation would not see that a 'new'
-  # package is being installed.
-  if [[ ${#CROS_WORKON_PKGS[@]} -gt 0 ]]; then
-    SIM_EMERGE_FLAGS+=(
-      --reinstall-atoms="${CROS_WORKON_PKGS[*]}"
-      --usepkg-exclude="${CROS_WORKON_PKGS[*]}"
-    )
-  fi
-
-  # Calculate only the ebuild changes from the emerge simulation ignoring
-  # the virtual packages and the forced rebuild of autotest-all package.
-  # The lines of the following block do the following operations:
-  # 1. Do a pretend `emerge` command to get a list of what would be built.
-  # 2. Filter to only packages that will be installed to the board sysroot.
-  # 3. Filter to only packages that would be built from source and rewrite the
-  #    line from Portage's full output to only $CATEGORY/$PACKAGE
-  # 4. Filter the list of packages to a heuristic set of packages known to have
-  #    incorrectly specified dependencies.
-  # 5. Sort the output and remove any duplicate entries.
-  BASE_INSTALL_PKGS=( $( \
-    sudo -E "${EMERGE_CMD[@]}" "${SIM_EMERGE_FLAGS[@]}" "${PACKAGES[@]}" | \
-    grep -e 'to /build/' | \
-    sed -n -E '/^\[ebuild /{s:^[^]]+\] +::;s: .*::;p}' | \
-    grep -E '/(coreboot-private-files.*|tast-build-deps)$' | \
-    sort -u ) )
-
-  MOD_PKGS=()
-  if [[ "${#BASE_INSTALL_PKGS[@]}" -gt 0 ]]; then
-    info "Forced rebuild packages detected: ${BASE_INSTALL_PKGS[*]}."
-    # Convert specific versions into base package names
-    MOD_PKGS+=( $(\
-    equery-${FLAGS_board} list -p -o --format='$category/$name' \
-      "${BASE_INSTALL_PKGS[@]}" | sort -u ) )
-    # Remove Chrome as rebuilding it is expensive and almost never makes sense.
-    # Ignore grep exit status in case chromeos-chrome is the only package.
-    grep_cmd=( grep -v )
-    for pkg in "${CHROME_PACKAGES[@]}"; do
-      grep_cmd+=( -e "${pkg}" )
-    done
-    MOD_PKGS=( $(printf '%s\n' "${MOD_PKGS[@]}" | "${grep_cmd[@]}" || :) )
-  fi
-
-  FORCE_LOCAL_BUILD_PKGS+=( "${MOD_PKGS[@]}" )
-
-  if [[ "${#MOD_PKGS[@]}" -gt 0 ]]; then
-    info "calculating reverse dependencies on packages: ${MOD_PKGS[*]}"
-    REV_DEPS=( $(\
-      equery-${FLAGS_board} -q depends --indirect "${MOD_PKGS[@]}" |\
-      awk '{print $1}' | grep -v ^virtual/ | sort -u) )
-    if [[ "${#REV_DEPS[@]}" -gt 0 ]]; then
-      # Convert specific versions into base package names
-      RMOD_PKGS=( $(\
-        equery-${FLAGS_board} -q list -p -o --format='$category/$name' \
-        "${REV_DEPS[@]}" | sort -u ) )
-      # Remove Chrome as rebuilding it is expensive and almost never makes
-      # sense.  Ignore grep exit status in case chromeos-chrome is the only
-      # package.
-      grep_cmd=( grep -v )
-      for pkg in "${CHROME_PACKAGES[@]}"; do
-        grep_cmd+=( -e "${pkg}" )
-      done
-      RMOD_PKGS=( $(printf '%s\n' "${RMOD_PKGS[@]}" | "${grep_cmd[@]}" || :) )
-      info "final reverse dependencies that will be rebuilt: ${RMOD_PKGS[*]}"
-      FORCE_LOCAL_BUILD_PKGS+=( "${RMOD_PKGS[@]}" )
-    fi
-  fi
-fi # end FLAGS_withrevdeps
-
-if [[ ${#FORCE_LOCAL_BUILD_PKGS[@]} -gt 0 ]]; then
-  EMERGE_FLAGS+=(
-    --reinstall-atoms="${FORCE_LOCAL_BUILD_PKGS[*]}"
-    --usepkg-exclude="${FORCE_LOCAL_BUILD_PKGS[*]}"
-  )
-fi
-
-# A list of critical system packages that should never be incidentally
-# reinstalled as a side effect of build_packages. All packages in this list
-# are special cased to prefer matching installed versions, overriding the
-# typical logic of upgrading to the newest available version.
-#
-# This list can't include any package that gets installed to a board!
-# Packages such as LLVM or binutils must not be in this list as the normal
-# rebuild logic must still apply to them for board targets.
-#
-# TODO(crbug/1050752): Remove this list and the corresponding arguments
-# to `emerge` below once we figure out how to exclude toolchain packages from
-# being upgraded transitively via BDEPEND relations.
-CRITICAL_SDK_PACKAGES=(
-  "dev-lang/rust"
-  "dev-lang/go"
-  "sys-libs/glibc"
-  "sys-devel/gcc"
-)
-
-info "Merging board packages now"
-(
-
-  # Start reproxy for remote execution of building chrome.
-  if [[ "${FLAGS_run_remoteexec}" -eq "${FLAGS_TRUE}" ]]; then
-    info "Starting RBE reproxy."
-    bootstrap="'${RECLIENT_DIR}/boostrap' --cfg='${REPROXY_CFG}' \
-      --re_proxy='${RECLIENT_DIR}/reproxy'"
-    ${boostrap}
-    trap "${boostrap} --shutdown" EXIT
-  # Support goma on bots. This has to run in subshell, otherwise EXIT trap
-  # handler is overwritten.
-  elif [[ "${FLAGS_run_goma}" -eq "${FLAGS_TRUE}" ]]; then
-    info "Starting goma compiler_proxy."
-    goma_ctl="${GOMA_DIR:-${HOME}/goma}/goma_ctl.py"
-    "${goma_ctl}" restart
-    trap "'${goma_ctl}' stop" EXIT
-  fi
-
-  info_run sudo -E "${EMERGE_CMD[@]}" "${EMERGE_FLAGS[@]}" "${PACKAGES[@]}" \
-    --useoldpkg-atoms="${CRITICAL_SDK_PACKAGES[*]}" \
-    --rebuild-exclude="${CRITICAL_SDK_PACKAGES[*]}"
-)
-
-echo "Builds complete"
-
-if [[ ${FLAGS_withdebugsymbols} -eq ${FLAGS_TRUE} ]]; then
-  info "fetching the debug symbols"
-  info_run sudo -E "${CHROMITE_BIN}/cros_install_debug_syms" \
-    "--board=${FLAGS_board}" "--all"
-fi
-
-command_completed
-echo "Done"
diff --git a/build_packages.sh b/build_packages.sh
new file mode 100644
index 0000000..ed6e804
--- /dev/null
+++ b/build_packages.sh
@@ -0,0 +1,548 @@
+#!/bin/bash
+
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This script is being deprecated and moved to chromite/ by 2022-06-30.
+# Do not add any references to this script.
+# Please reach out if you have any questions.
+
+. "$(dirname "$0")/common.sh" || exit 1
+
+if [[ "$1" != "--script-is-run-only-by-chromite-and-not-users" ]]; then
+  die_notrace 'This script must not be run by users.' \
+    'Please run `build_packages` from $PATH (in chromite/bin/) instead.'
+fi
+# Discard the magic marker flag.
+shift
+
+# Script must run inside the chroot
+restart_in_chroot_if_needed "$@"
+
+assert_not_root_user
+
+# Developer-visible flags.
+DEFINE_string board "${DEFAULT_BOARD}" \
+  "The board to build packages for."
+DEFINE_boolean usepkg "${FLAGS_TRUE}" \
+  "Use binary packages to bootstrap when possible."
+DEFINE_boolean usepkgonly "${FLAGS_FALSE}" \
+  "Only use binary packages to bootstrap; abort if any are missing."
+DEFINE_boolean workon "${FLAGS_TRUE}" \
+  "Force-build workon packages."
+DEFINE_boolean showoutput "${FLAGS_FALSE}" \
+  "Show all output from parallel_emerge."
+DEFINE_boolean withautotest "${FLAGS_TRUE}" \
+  "Build autotest client code."
+DEFINE_boolean withdebugsymbols "${FLAGS_FALSE}" \
+  "Install the debug symbols for all packages"
+DEFINE_boolean withrevdeps "${FLAGS_TRUE}" \
+  "Calculate reverse dependencies on changed ebuilds."
+DEFINE_boolean autosetgov "${FLAGS_FALSE}" \
+  "Automatically set cpu governor to 'performance'."
+DEFINE_boolean autosetgov_sticky "${FLAGS_FALSE}" \
+  "Remember --autosetgov setting for future runs."
+DEFINE_boolean use_any_chrome "${FLAGS_TRUE}" \
+  "Use any Chrome prebuilt available, even if the prebuilt doesn't match exactly."
+DEFINE_boolean cleanbuild "${FLAGS_FALSE}" \
+  "Perform a clean build; delete sysroot if it exists before building."
+DEFINE_boolean internal "${FLAGS_FALSE}" \
+  "Build the internal version of chrome (set the chrome_internal USE flag)."
+DEFINE_boolean pretend "${FLAGS_FALSE}" \
+  "Don't build packages, just display which packages would have been installed."
+
+# The --board_root flag specifies the environment variables ROOT and PKGDIR.
+# This allows fetching and emerging of all packages to specified board_root.
+# Note that --board_root will setup the board normally in /build/$BOARD, if it's
+# not setup yet. It also expects the toolchain to already be installed in the
+# board_root. --usepkgonly and --norebuild are required, because building is not
+# supported when board_root is set.
+# enforce this)."
+DEFINE_string board_root "" \
+  "Emerge packages to board_root."
+
+FLAGS_HELP="usage: $(basename $0) [flags] [packages]
+
+build_packages updates the set of binary packages needed by Chrome OS. It will
+cross compile all packages that have been updated into the given target's root
+and build binary packages as a side-effect. The output packages will be picked
+up by the build_image script to put together a bootable Chrome OS image.
+
+If [packages] are specified, only build those specific packages (and any
+dependencies they might need).
+
+For the fastest builds, use --nowithautotest --noworkon.
+"
+
+# The following options are advanced options, only available to those willing
+# to read the source code. They are not shown in help output, since they are
+# not needed for the typical developer workflow.
+DEFINE_string accept_licenses "" \
+  "Licenses to append to the accept list."
+DEFINE_boolean eclean "${FLAGS_TRUE}" \
+  "Run eclean to delete old binpkgs."
+DEFINE_integer jobs -1 \
+  "How many packages to build in parallel at maximum."
+DEFINE_boolean norebuild "${FLAGS_FALSE}" \
+  "Don't automatically rebuild dependencies."
+DEFINE_boolean skip_chroot_upgrade "${FLAGS_FALSE}" \
+  "Don't run the chroot upgrade automatically; use with care."
+DEFINE_boolean skip_setup_board "${FLAGS_FALSE}" \
+  "Don't run setup_board. Implies skip_chroot_upgrade and" \
+  "skip_toolchain_update."
+DEFINE_boolean skip_toolchain_update "${FLAGS_FALSE}" \
+  "Don't update toolchain automatically."
+DEFINE_boolean withdev "${FLAGS_TRUE}" \
+  "Build useful developer friendly utilities."
+DEFINE_boolean withdebug "${FLAGS_TRUE}" \
+  "Build debug versions of Chromium-OS-specific packages."
+DEFINE_boolean withfactory "${FLAGS_TRUE}" \
+  "Build factory installer."
+DEFINE_boolean withtest "${FLAGS_TRUE}" \
+  "Build packages required for testing."
+DEFINE_boolean expandedbinhosts "${FLAGS_TRUE}" \
+  "Allow expanded binhost inheritance."
+
+# The --reuse_pkgs_from_local_boards flag tells Portage to share binary
+# packages between boards that are built locally, so that the total time
+# required to build several boards is reduced. This flag is only useful
+# when you are not able to use remote binary packages, since remote binary
+# packages are usually more up to date than anything you have locally.
+DEFINE_boolean reuse_pkgs_from_local_boards "${FLAGS_FALSE}" \
+  "Bootstrap from local packages instead of remote packages."
+
+# --run_goma option is designed to be used on bots.
+# If you're trying to build pacakges with goma in your local dev env, this is
+# *not* the option you're looking for. Please see comments below.
+# This option; 1) starts goma, 2) builds packages (expecting that goma is
+# used), then 3) stops goma explicitly.
+# 3) is a request from the goma team, so that stats/logs can be taken.
+# Note: GOMA_DIR and GOMA_SERVICE_ACCOUNT_JSON_FILE are expected to be passed
+# via env var.
+#
+# In local dev env cases, compiler_proxy is expected to keep running.
+# In such a case;
+#   $ python ${GOMA_DIR}/goma_ctl.py ensure_start
+#   $ ./build_packages (... and options without --run_goma ...)
+# is an expected commandline sequence. If you set --run_goma flag while
+# compiler_proxy is already running, the existing compiler_proxy will be
+# stopped.
+DEFINE_boolean run_goma "${FLAGS_FALSE}" \
+  "If set to true, (re)starts goma, builds packages, and then stops goma."
+
+# This option is for building chrome remotely.
+#1) starts reproxy 2) builds chrome with reproxy and 3) stops reproxy so
+# logs/stats can be collected.
+# Note: RECLIENT_DIR and REPROXY_CFG are expected to be passed via env var.
+DEFINE_boolean run_remoteexec "${FLAGS_FALSE}" \
+  "If set to true, starts RBE reproxy, builds packages, and then stops reproxy."
+
+# Parse command line
+FLAGS "$@" || exit 1
+eval set -- "${FLAGS_ARGV}"
+
+# Die on any errors.
+switch_to_strict_mode
+
+# Chrome packages that need to be treated the same. These are the chrome and
+# chrome follow-on packages that share the same version as chrome and are
+# updated in lock step.
+CHROME_PACKAGES=(
+  "chromeos-base/chromeos-chrome"
+  "chromeos-base/chrome-icu"
+)
+
+if [[ "${FLAGS_internal}" -eq "${FLAGS_TRUE}" ]]; then
+  export USE="${USE} chrome_internal"
+fi
+
+# Right now build_packages has to be run from scripts/
+. ${SRC_ROOT}/third_party/chromiumos-overlay/chromeos/config/chromeos_version.sh
+
+# On some systems, powersave can take a long time to ramp up.  Inform the user
+# so they can get faster builds.  https://crbug.com/1008932
+CHROMITE_CONFIG_DIR=$(
+  python -c 'from chromite.lib.chromite_config import DIR; print(DIR)')
+CONFIG_AUTOSETGOV="${CHROMITE_CONFIG_DIR}/autosetgov"
+if [[ "${FLAGS_autosetgov_sticky}" -eq "${FLAGS_TRUE}" ]]; then
+  mkdir -p "${CHROMITE_CONFIG_DIR}"
+  if [[ "${FLAGS_autosetgov}" -eq "${FLAGS_TRUE}" ]]; then
+    info "Future runs of build_packages will *always* use --autosetgov"
+    echo "# Delete this file to turn off automatic build_packages" \
+      "--autosetgov." >"${CONFIG_AUTOSETGOV}"
+  else
+    info "Future runs of build_packages will respect --autosetgov"
+    rm -f "${CONFIG_AUTOSETGOV}"
+  fi
+fi
+if [[ -e "${CONFIG_AUTOSETGOV}" ]]; then
+  FLAGS_autosetgov="${FLAGS_TRUE}"
+fi
+# Make sure we can actually support "performance".
+if grep -qs performance \
+     /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors; then
+  curr_gov=$(sort -u /sys/devices/system/cpu/cpufreq/policy*/scaling_governor)
+  if [[ "${curr_gov}" != "performance" ]]; then
+    if [[ "${FLAGS_autosetgov}" -eq "${FLAGS_TRUE}" ]]; then
+      if [[ $(echo "${curr_gov}" | wc -l) -gt 1 ]]; then
+        warn "Too many active CPU governors; refusing to use 'performance'."
+      else
+        info "Temporarily setting cpu governor to 'performance'"
+        trap "sudo cpupower -c all frequency-set -g powersave >&/dev/null" EXIT
+        sudo cpupower -c all frequency-set -g performance >&/dev/null
+      fi
+    elif [[ "${curr_gov}" == "powersave" ]]; then
+      warn "Current CPU governor set to 'powersave' which can slow down builds."
+      warn "Use --autosetgov to automatically (and temporarily) switch to" \
+        "'performance'."
+    fi
+  fi
+fi
+
+if [[ -z "${FLAGS_board}" ]]; then
+  echo "Error: --board is required."
+  exit 1
+fi
+
+BOARD_ROOT="${FLAGS_board_root:-/build/${FLAGS_board}}"
+
+# Skip revdeps when we don't already have a built sysroot.
+if [[ "${FLAGS_cleanbuild}" -eq "${FLAGS_TRUE}" || ! -d "${BOARD_ROOT}" ]]; then
+  SKIP_REVDEPS="${FLAGS_TRUE}"
+else
+  SKIP_REVDEPS="${FLAGS_FALSE}"
+fi
+
+if [[ "${FLAGS_skip_setup_board}" -eq "${FLAGS_FALSE}" ]]; then
+  # Before we can run any tools, we need to update chroot or setup_board.
+  UPDATE_ARGS=()
+  if [[ -n ${FLAGS_accept_licenses} ]]; then
+    UPDATE_ARGS+=( --accept-licenses "${FLAGS_accept_licenses}" )
+  fi
+  if [ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ]; then
+    UPDATE_ARGS+=( --usepkg )
+  else
+    UPDATE_ARGS+=( --nousepkg )
+  fi
+  if [[ "${FLAGS_jobs}" -ne -1 ]]; then
+    UPDATE_ARGS+=( --jobs=${FLAGS_jobs} )
+  fi
+  if [ "${FLAGS_reuse_pkgs_from_local_boards}" -eq "${FLAGS_TRUE}" ]; then
+    UPDATE_ARGS+=( --reuse-pkgs-from-local-boards )
+  fi
+  if [ "${FLAGS_skip_toolchain_update}" -eq "${FLAGS_TRUE}" ]; then
+    UPDATE_ARGS+=( --skip-toolchain-update )
+  fi
+  if [ "${FLAGS_skip_chroot_upgrade}" -eq "${FLAGS_TRUE}" ]; then
+    UPDATE_ARGS+=( --skip-chroot-upgrade )
+  fi
+  if [[ -n ${FLAGS_board_root} ]]; then
+    UPDATE_ARGS+=( --board-root "${FLAGS_board_root}" )
+  fi
+  if [ "${FLAGS_cleanbuild}" -eq "${FLAGS_TRUE}" ]; then
+    UPDATE_ARGS+=( --force )
+  fi
+  if [[ "${FLAGS_expandedbinhosts}" -eq "${FLAGS_FALSE}" ]]; then
+    UPDATE_ARGS+=( --fewer-binhosts )
+  fi
+
+  setup_board --quiet --board=${FLAGS_board} "${UPDATE_ARGS[@]}"
+fi
+
+sudo_clear_shadow_locks "${BOARD_ROOT}"
+PORTAGE_BINHOST=$(portageq-${FLAGS_board} envvar 'PORTAGE_BINHOST')
+info "PORTAGE_BINHOST: ${PORTAGE_BINHOST}"
+
+
+# Setup all the emerge command/flags.
+EMERGE_FLAGS=( -uDNv --backtrack=30 --newrepo --with-test-deps y )
+
+EMERGE_CMD=(
+  "${CHROMITE_BIN}/parallel_emerge"
+  --board=${FLAGS_board}
+)
+
+if [[ "${FLAGS_use_any_chrome}" -eq "${FLAGS_TRUE}" ]]; then
+  for pkg in "${CHROME_PACKAGES[@]}"; do
+    EMERGE_CMD+=( "--force-remote-binary=${pkg}" )
+  done
+fi
+
+EMERGE_CMD+=( ${EXTRA_BOARD_FLAGS} )
+
+if [[ "${FLAGS_pretend}" -eq "${FLAGS_TRUE}" ]]; then
+  EMERGE_FLAGS+=( "--pretend" )
+fi
+
+if [[ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ||
+      "${FLAGS_reuse_pkgs_from_local_boards}" -eq "${FLAGS_TRUE}" ||
+      "${FLAGS_usepkgonly}" -eq "${FLAGS_TRUE}" ]]; then
+  # Use binary packages. Include all build-time dependencies,
+  # so as to avoid unnecessary differences between source
+  # and binary builds.
+  EMERGE_FLAGS+=( --getbinpkg --with-bdeps y )
+  if [[ ${FLAGS_usepkgonly} -eq ${FLAGS_TRUE} ]]; then
+    EMERGE_FLAGS+=( --usepkgonly )
+  else
+    EMERGE_FLAGS+=( --usepkg )
+  fi
+fi
+
+if [[ "${FLAGS_jobs}" -ne -1 ]]; then
+  EMERGE_FLAGS+=( --jobs=${FLAGS_jobs} )
+fi
+
+if [[ "${FLAGS_norebuild}" -eq "${FLAGS_FALSE}" ]]; then
+  EMERGE_FLAGS+=( --rebuild-if-new-rev )
+fi
+if [[ "${FLAGS_showoutput}" -eq "${FLAGS_TRUE}" ]]; then
+  EMERGE_FLAGS+=( --show-output )
+fi
+
+if [[ "${FLAGS_withdebug}" -eq "${FLAGS_FALSE}" ]]; then
+  export USE="${USE} -cros-debug"
+fi
+
+# Figure out which packages we should be building.
+PACKAGES=( "$@" )
+FORCE_LOCAL_BUILD_PKGS=()
+if [[ $# -eq 0 ]]; then
+  PACKAGES=( virtual/target-os )
+  if [[ "${FLAGS_withdev}" -eq "${FLAGS_TRUE}" ]]; then
+    PACKAGES+=( virtual/target-os-dev )
+  fi
+  if [[ "${FLAGS_withfactory}" -eq "${FLAGS_TRUE}" ]]; then
+    PACKAGES+=( virtual/target-os-factory )
+    PACKAGES+=( virtual/target-os-factory-shim )
+  fi
+  if [[ "${FLAGS_withtest}" -eq "${FLAGS_TRUE}" ]]; then
+    PACKAGES+=( virtual/target-os-test )
+    # chromeos-ssh-testkeys may generate ssh keys if the right USE flag is set.
+    # We force rebuilding this package from source every time, so that
+    # consecutive builds don't share ssh keys.
+    FORCE_LOCAL_BUILD_PKGS+=( chromeos-base/chromeos-ssh-testkeys )
+  fi
+  if [[ "${FLAGS_withautotest}" -eq "${FLAGS_TRUE}" ]]; then
+    PACKAGES+=( chromeos-base/autotest-all )
+  fi
+fi
+
+info "Rebuilding Portage cache"
+# Before running any emerge operations, regenerate the Portage dependency cache
+# in parallel.
+info_run "${EMERGE_CMD[@]}" --regen --quiet
+
+# Clean out any stale binpkgs we've accumulated. This is done immediately after
+# regenerating the cache in case ebuilds have been removed (e.g. from a revert).
+if [[ "${FLAGS_eclean}" -eq "${FLAGS_TRUE}" ]]; then
+  info "Cleaning stale binpkgs"
+  get_eclean_exclusions | "eclean-${FLAGS_board}" -e /dev/stdin packages
+fi
+
+# Verify that all packages can be emerged from scratch, without any
+# backtracking. Only print the output if this step fails.
+info "Checking package dependencies are correct: ${PACKAGES[*]}"
+if ! OUTPUT=$(emerge-${FLAGS_board} -pe --backtrack=0 \
+              "${PACKAGES[@]}" 2>&1); then
+  printf "%s\n" "${OUTPUT}"
+  die_notrace "emerge detected broken ebuilds. See error message above."
+fi
+
+# Build cros_workon packages when they are changed.
+CROS_WORKON_PKGS=()
+if [ "${FLAGS_workon}" -eq "${FLAGS_TRUE}" ]; then
+  LIST_MODIFIED_PACKAGES="${CHROMITE_BIN}/cros_list_modified_packages"
+  MODIFIED_PACKAGES=( $("${LIST_MODIFIED_PACKAGES}" --board=${FLAGS_board}) )
+  info "cros_workon modified packages '${MODIFIED_PACKAGES[*]}' detected"
+  CROS_WORKON_PKGS+=( "${MODIFIED_PACKAGES[@]}" )
+
+  # TODO(anush): Make chrome a fake cros-workon package.
+  if [[ -n "${CHROME_ORIGIN}" ]]; then
+    CROS_WORKON_PKGS+=( "${CHROME_PACKAGES[@]}" )
+  fi
+fi
+
+# cros_workon packages always have to be rebuilt.
+FORCE_LOCAL_BUILD_PKGS+=( "${CROS_WORKON_PKGS[@]}" )
+
+# Any package that directly depends on an active cros_workon package also needs
+# to be rebuilt in order to be correctly built against the current set of
+# changes a user may have made to the cros_workon package.
+if [[ ${#CROS_WORKON_PKGS[@]} -gt 0 ]]; then
+  # Collect all installed packages that depend on active cros_workon packages.
+  WORKON_PKG_CONSUMERS=()
+  mapfile -t WORKON_PKG_CONSUMERS < <( \
+    equery-${FLAGS_board} -q depends "${CROS_WORKON_PKGS[@]}" | \
+    sort -u | \
+    grep -Ev "^\s*$" )
+
+  # Transform this list of packages with versions in to a list of just
+  # $CATEGORY/$NAME entries, since we don't want to pass packages with explicit
+  # version numbers as arguments to `emerge`.
+  if [[ ${#WORKON_PKG_CONSUMERS[@]} -gt 0 ]]; then
+    WORKON_REBUILD_PKGS=()
+    mapfile -t WORKON_REBUILD_PKGS < <( \
+      equery-${FLAGS_board} list -p -o --format='$category/$name' \
+        "${WORKON_PKG_CONSUMERS[@]}" | sort -u )
+
+    info "The following packages depend directly on an active" \
+      "cros_workon package and will be rebuilt: ${WORKON_REBUILD_PKGS[*]}"
+
+    FORCE_LOCAL_BUILD_PKGS+=( "${WORKON_REBUILD_PKGS[@]}" )
+  fi
+fi
+
+if [[ -n "${FLAGS_board_root}" ]]; then
+  export ROOT="${FLAGS_board_root}"
+  export PORTAGE_CONFIGROOT="${ROOT}"
+  export SYSROOT="${ROOT}"
+  export PKGDIR="${ROOT}"/packages
+fi
+
+# Temporarily modify the emerge flags so we can calculate the revdeps
+# on the modified packages.
+if [[ "${FLAGS_withrevdeps}" -eq "${FLAGS_TRUE}" &&
+      "${SKIP_REVDEPS}" -eq "${FLAGS_FALSE}" ]]; then
+  info "starting reverse dependency calculations ..."
+  SIM_EMERGE_FLAGS=( "${EMERGE_FLAGS[@]}" --pretend --columns )
+
+  if [[ ${#PACKAGES[@]} -gt 0 ]]; then
+    SIM_EMERGE_FLAGS+=(
+      --reinstall-atoms="${PACKAGES[*]}"
+      --usepkg-exclude="${PACKAGES[*]}"
+    )
+  fi
+
+  # cros-workon packages are always going to be force reinstalled, so we add
+  # the forced reinstall behavior to the modified package calculation. This is
+  # necessary to include when a user has already installed a 9999 ebuild and is
+  # now reinstalling that package with additional local changes, because
+  # otherwise the modified package calculation would not see that a 'new'
+  # package is being installed.
+  if [[ ${#CROS_WORKON_PKGS[@]} -gt 0 ]]; then
+    SIM_EMERGE_FLAGS+=(
+      --reinstall-atoms="${CROS_WORKON_PKGS[*]}"
+      --usepkg-exclude="${CROS_WORKON_PKGS[*]}"
+    )
+  fi
+
+  # Calculate only the ebuild changes from the emerge simulation ignoring
+  # the virtual packages and the forced rebuild of autotest-all package.
+  # The lines of the following block do the following operations:
+  # 1. Do a pretend `emerge` command to get a list of what would be built.
+  # 2. Filter to only packages that will be installed to the board sysroot.
+  # 3. Filter to only packages that would be built from source and rewrite the
+  #    line from Portage's full output to only $CATEGORY/$PACKAGE
+  # 4. Filter the list of packages to a heuristic set of packages known to have
+  #    incorrectly specified dependencies.
+  # 5. Sort the output and remove any duplicate entries.
+  BASE_INSTALL_PKGS=( $( \
+    sudo -E "${EMERGE_CMD[@]}" "${SIM_EMERGE_FLAGS[@]}" "${PACKAGES[@]}" | \
+    grep -e 'to /build/' | \
+    sed -n -E '/^\[ebuild /{s:^[^]]+\] +::;s: .*::;p}' | \
+    grep -E '/(coreboot-private-files.*|tast-build-deps)$' | \
+    sort -u ) )
+
+  MOD_PKGS=()
+  if [[ "${#BASE_INSTALL_PKGS[@]}" -gt 0 ]]; then
+    info "Forced rebuild packages detected: ${BASE_INSTALL_PKGS[*]}."
+    # Convert specific versions into base package names
+    MOD_PKGS+=( $(\
+    equery-${FLAGS_board} list -p -o --format='$category/$name' \
+      "${BASE_INSTALL_PKGS[@]}" | sort -u ) )
+    # Remove Chrome as rebuilding it is expensive and almost never makes sense.
+    # Ignore grep exit status in case chromeos-chrome is the only package.
+    grep_cmd=( grep -v )
+    for pkg in "${CHROME_PACKAGES[@]}"; do
+      grep_cmd+=( -e "${pkg}" )
+    done
+    MOD_PKGS=( $(printf '%s\n' "${MOD_PKGS[@]}" | "${grep_cmd[@]}" || :) )
+  fi
+
+  FORCE_LOCAL_BUILD_PKGS+=( "${MOD_PKGS[@]}" )
+
+  if [[ "${#MOD_PKGS[@]}" -gt 0 ]]; then
+    info "calculating reverse dependencies on packages: ${MOD_PKGS[*]}"
+    REV_DEPS=( $(\
+      equery-${FLAGS_board} -q depends --indirect "${MOD_PKGS[@]}" |\
+      awk '{print $1}' | grep -v ^virtual/ | sort -u) )
+    if [[ "${#REV_DEPS[@]}" -gt 0 ]]; then
+      # Convert specific versions into base package names
+      RMOD_PKGS=( $(\
+        equery-${FLAGS_board} -q list -p -o --format='$category/$name' \
+        "${REV_DEPS[@]}" | sort -u ) )
+      # Remove Chrome as rebuilding it is expensive and almost never makes
+      # sense.  Ignore grep exit status in case chromeos-chrome is the only
+      # package.
+      grep_cmd=( grep -v )
+      for pkg in "${CHROME_PACKAGES[@]}"; do
+        grep_cmd+=( -e "${pkg}" )
+      done
+      RMOD_PKGS=( $(printf '%s\n' "${RMOD_PKGS[@]}" | "${grep_cmd[@]}" || :) )
+      info "final reverse dependencies that will be rebuilt: ${RMOD_PKGS[*]}"
+      FORCE_LOCAL_BUILD_PKGS+=( "${RMOD_PKGS[@]}" )
+    fi
+  fi
+fi # end FLAGS_withrevdeps
+
+if [[ ${#FORCE_LOCAL_BUILD_PKGS[@]} -gt 0 ]]; then
+  EMERGE_FLAGS+=(
+    --reinstall-atoms="${FORCE_LOCAL_BUILD_PKGS[*]}"
+    --usepkg-exclude="${FORCE_LOCAL_BUILD_PKGS[*]}"
+  )
+fi
+
+# A list of critical system packages that should never be incidentally
+# reinstalled as a side effect of build_packages. All packages in this list
+# are special cased to prefer matching installed versions, overriding the
+# typical logic of upgrading to the newest available version.
+#
+# This list can't include any package that gets installed to a board!
+# Packages such as LLVM or binutils must not be in this list as the normal
+# rebuild logic must still apply to them for board targets.
+#
+# TODO(crbug/1050752): Remove this list and the corresponding arguments
+# to `emerge` below once we figure out how to exclude toolchain packages from
+# being upgraded transitively via BDEPEND relations.
+CRITICAL_SDK_PACKAGES=(
+  "dev-lang/rust"
+  "dev-lang/go"
+  "sys-libs/glibc"
+  "sys-devel/gcc"
+)
+
+info "Merging board packages now"
+(
+
+  # Start reproxy for remote execution of building chrome.
+  if [[ "${FLAGS_run_remoteexec}" -eq "${FLAGS_TRUE}" ]]; then
+    info "Starting RBE reproxy."
+    bootstrap="'${RECLIENT_DIR}/boostrap' --cfg='${REPROXY_CFG}' \
+      --re_proxy='${RECLIENT_DIR}/reproxy'"
+    ${boostrap}
+    trap "${boostrap} --shutdown" EXIT
+  # Support goma on bots. This has to run in subshell, otherwise EXIT trap
+  # handler is overwritten.
+  elif [[ "${FLAGS_run_goma}" -eq "${FLAGS_TRUE}" ]]; then
+    info "Starting goma compiler_proxy."
+    goma_ctl="${GOMA_DIR:-${HOME}/goma}/goma_ctl.py"
+    "${goma_ctl}" restart
+    trap "'${goma_ctl}' stop" EXIT
+  fi
+
+  info_run sudo -E "${EMERGE_CMD[@]}" "${EMERGE_FLAGS[@]}" "${PACKAGES[@]}" \
+    --useoldpkg-atoms="${CRITICAL_SDK_PACKAGES[*]}" \
+    --rebuild-exclude="${CRITICAL_SDK_PACKAGES[*]}"
+)
+
+echo "Builds complete"
+
+if [[ ${FLAGS_withdebugsymbols} -eq ${FLAGS_TRUE} ]]; then
+  info "fetching the debug symbols"
+  info_run sudo -E "${CHROMITE_BIN}/cros_install_debug_syms" \
+    "--board=${FLAGS_board}" "--all"
+fi
+
+command_completed
+echo "Done"