build_packages: Remove showoutput argument support

The argument showoutput and its related arguments are deprecated. Remove
its support.

BUG=b:229258065
TEST=run_tests lib/ service/ scripts/

Change-Id: I20e18a8caae7fa8882aed7b67ac72e28cc4a3eca
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3582735
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Ram Chandrasekar <rchandrasekar@google.com>
Tested-by: Ram Chandrasekar <rchandrasekar@google.com>
Auto-Submit: Ram Chandrasekar <rchandrasekar@google.com>
diff --git a/build_packages.sh b/build_packages.sh
index e8dc659..be45b39 100644
--- a/build_packages.sh
+++ b/build_packages.sh
@@ -26,8 +26,6 @@
   "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}" \
@@ -166,9 +164,6 @@
 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
 
 # Figure out which packages we should be building.
 PACKAGES=( "$@" )