doebuild: update environment.bz2 for pre/postinst

Also, remove unnecessary __dyn_preinst func.
diff --git a/bin/misc-functions.sh b/bin/misc-functions.sh
index 486b8d2..1159ca5 100755
--- a/bin/misc-functions.sh
+++ b/bin/misc-functions.sh
@@ -1082,7 +1082,7 @@
 		 return 1
 	fi
 	if has selinux ${FEATURES}; then
-		# SELinux file labeling (needs to always be last in __dyn_preinst)
+		# SELinux file labeling (needs to execute after preinst)
 		# only attempt to label if setfiles is executable
 		# and 'context' is available on selinuxfs.
 		if [ -f /selinux/context -o -f /sys/fs/selinux/context ] && \
diff --git a/bin/phase-functions.sh b/bin/phase-functions.sh
index 7048419..92e25c6 100644
--- a/bin/phase-functions.sh
+++ b/bin/phase-functions.sh
@@ -601,14 +601,6 @@
 	trap - SIGINT SIGQUIT
 }
 
-__dyn_preinst() {
-	if [ -z "${D}" ]; then
-		eerror "${FUNCNAME}: D is unset"
-		return 1
-	fi
-	__ebuild_phase_with_hooks pkg_preinst
-}
-
 __dyn_help() {
 	echo
 	echo "Portage"
@@ -871,7 +863,7 @@
 	nofetch)
 		__ebuild_phase_with_hooks pkg_nofetch
 		;;
-	prerm|postrm|postinst|config|info)
+	prerm|postrm|preinst|postinst|config|info)
 		if has "${1}" config info && \
 			! declare -F "pkg_${1}" >/dev/null ; then
 			ewarn  "pkg_${1}() is not defined: '${EBUILD##*/}'"
@@ -884,7 +876,7 @@
 			__ebuild_phase_with_hooks pkg_${1}
 			set +x
 		fi
-		if [[ $EBUILD_PHASE == postinst ]] && [[ -n $PORTAGE_UPDATE_ENV ]]; then
+		if [[ -n $PORTAGE_UPDATE_ENV ]] ; then
 			# Update environment.bz2 in case installation phases
 			# need to pass some variables to uninstallation phases.
 			__save_ebuild_env --exclude-init-phases | \
@@ -960,7 +952,7 @@
 		fi
 		export SANDBOX_ON="0"
 		;;
-	help|pretend|setup|preinst)
+	help|pretend|setup)
 		#pkg_setup needs to be out of the sandbox for tmp file creation;
 		#for example, awking and piping a file in /tmp requires a temp file to be created
 		#in /etc.  If pkg_setup is in the sandbox, both our lilo and apache ebuilds break.
diff --git a/bin/save-ebuild-env.sh b/bin/save-ebuild-env.sh
index de8e1fb..7ae3938 100644
--- a/bin/save-ebuild-env.sh
+++ b/bin/save-ebuild-env.sh
@@ -63,7 +63,7 @@
 		__abort_handler __abort_prepare __abort_configure __abort_compile \
 		__abort_test __abort_install __dyn_prepare __dyn_configure \
 		__dyn_compile __dyn_test __dyn_install \
-		__dyn_preinst __dyn_pretend __dyn_help \
+		__dyn_pretend __dyn_help \
 		debug-print debug-print-function \
 		debug-print-section __helpers_die inherit EXPORT_FUNCTIONS \
 		nonfatal register_success_hook \
diff --git a/pym/portage/package/ebuild/doebuild.py b/pym/portage/package/ebuild/doebuild.py
index 89b6050..7200327 100644
--- a/pym/portage/package/ebuild/doebuild.py
+++ b/pym/portage/package/ebuild/doebuild.py
@@ -904,8 +904,16 @@
 		# the sandbox -- and stop now.
 		if mydo in ("config", "help", "info", "postinst",
 			"preinst", "pretend", "postrm", "prerm"):
-			return _spawn_phase(mydo, mysettings,
-				fd_pipes=fd_pipes, logfile=logfile, returnpid=returnpid)
+			if mydo in ("preinst", "postinst"):
+				env_file = os.path.join(os.path.dirname(mysettings["EBUILD"]),
+					"environment.bz2")
+				if os.path.isfile(env_file):
+					mysettings["PORTAGE_UPDATE_ENV"] = env_file
+			try:
+				return _spawn_phase(mydo, mysettings,
+					fd_pipes=fd_pipes, logfile=logfile, returnpid=returnpid)
+			finally:
+				mysettings.pop("PORTAGE_UPDATE_ENV", None)
 
 		mycpv = "/".join((mysettings["CATEGORY"], mysettings["PF"]))