diff --git a/sys-apps/portage/portage-3.0.30-r1.ebuild b/sys-apps/portage/portage-3.0.30-r1.ebuild
index 128c6819b0d94..590e0036a88a1 100644
--- a/sys-apps/portage/portage-3.0.30-r1.ebuild
+++ b/sys-apps/portage/portage-3.0.30-r1.ebuild
@@ -228,24 +228,26 @@ python_install_all() {
 }
 
 pkg_preinst() {
-	python_setup
-	local sitedir=$(python_get_sitedir)
-	[[ -d ${D}${sitedir} ]] || die "${D}${sitedir}: No such directory"
-	env -u DISTDIR \
-		-u PORTAGE_OVERRIDE_EPREFIX \
-		-u PORTAGE_REPOSITORIES \
-		-u PORTDIR \
-		-u PORTDIR_OVERLAY \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.default_locations || die
+	if ! use build; then
+		python_setup
+		local sitedir=$(python_get_sitedir)
+		[[ -d ${D}${sitedir} ]] || die "${D}${sitedir}: No such directory"
+		env -u DISTDIR \
+			-u PORTAGE_OVERRIDE_EPREFIX \
+			-u PORTAGE_REPOSITORIES \
+			-u PORTDIR \
+			-u PORTDIR_OVERLAY \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.default_locations || die
 
-	env -u BINPKG_COMPRESS -u PORTAGE_REPOSITORIES \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.binpkg_compression || die
+		env -u BINPKG_COMPRESS -u PORTAGE_REPOSITORIES \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.binpkg_compression || die
 
-	env -u FEATURES -u PORTAGE_REPOSITORIES \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.binpkg_multi_instance || die
+		env -u FEATURES -u PORTAGE_REPOSITORIES \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.binpkg_multi_instance || die
+	fi
 
 	# elog dir must exist to avoid logrotate error for bug #415911.
 	# This code runs in preinst in order to bypass the mapping of
diff --git a/sys-apps/portage/portage-9999.ebuild b/sys-apps/portage/portage-9999.ebuild
index 6db78dd658f78..c741638d18e9c 100644
--- a/sys-apps/portage/portage-9999.ebuild
+++ b/sys-apps/portage/portage-9999.ebuild
@@ -222,24 +222,26 @@ python_install_all() {
 }
 
 pkg_preinst() {
-	python_setup
-	local sitedir=$(python_get_sitedir)
-	[[ -d ${D}${sitedir} ]] || die "${D}${sitedir}: No such directory"
-	env -u DISTDIR \
-		-u PORTAGE_OVERRIDE_EPREFIX \
-		-u PORTAGE_REPOSITORIES \
-		-u PORTDIR \
-		-u PORTDIR_OVERLAY \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.default_locations || die
+	if ! use build; then
+		python_setup
+		local sitedir=$(python_get_sitedir)
+		[[ -d ${D}${sitedir} ]] || die "${D}${sitedir}: No such directory"
+		env -u DISTDIR \
+			-u PORTAGE_OVERRIDE_EPREFIX \
+			-u PORTAGE_REPOSITORIES \
+			-u PORTDIR \
+			-u PORTDIR_OVERLAY \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.default_locations || die
 
-	env -u BINPKG_COMPRESS -u PORTAGE_REPOSITORIES \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.binpkg_compression || die
+		env -u BINPKG_COMPRESS -u PORTAGE_REPOSITORIES \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.binpkg_compression || die
 
-	env -u FEATURES -u PORTAGE_REPOSITORIES \
-		PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
-		"${PYTHON}" -m portage._compat_upgrade.binpkg_multi_instance || die
+		env -u FEATURES -u PORTAGE_REPOSITORIES \
+			PYTHONPATH="${D}${sitedir}${PYTHONPATH:+:${PYTHONPATH}}" \
+			"${PYTHON}" -m portage._compat_upgrade.binpkg_multi_instance || die
+	fi
 
 	# elog dir must exist to avoid logrotate error for bug #415911.
 	# This code runs in preinst in order to bypass the mapping of