cros_update_firmware: Use parallel emerge

Use parallel emerge for firmware manifest build.

BUG=none
TEST=Test with zork f/w rebuild.

Change-Id: Iccad8bc10e5331ef8acaea39aab8a29707ad0e9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2297021
Tested-by: Andrew McRae <amcrae@chromium.org>
Auto-Submit: Andrew McRae <amcrae@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/contrib/cros_update_firmware b/contrib/cros_update_firmware
index 85309e7..9337242 100755
--- a/contrib/cros_update_firmware
+++ b/contrib/cros_update_firmware
@@ -110,7 +110,7 @@
     popd > /dev/null
   fi
 
-  "emerge-${board}" ${quiet} ${cfg_bsp_baseboard_pkg} "${cfg_bsp_pkg}" chromeos-config
+  "emerge-${board}" -j ${quiet} ${cfg_bsp_baseboard_pkg} "${cfg_bsp_pkg}" chromeos-config
   cros_config_host -c "${yaml_config}" get-firmware-uris > "${srcuris}"
   touch "${ebuild}"
 
@@ -123,7 +123,7 @@
   # these cache cleanup code.
   rm -rf "${metadata}/cache" "${metadata}/md5-cache" "${edb_cache}"
   "ebuild-${board}" "${ebuild}" manifest
-  "emerge-${board}" ${quiet} "chromeos-firmware-${board}"
+  "emerge-${board}" -j ${quiet} "chromeos-firmware-${board}"
 
   for i in "${!result[@]}"; do
     if [[ "${result[i]}" -eq "0" ]]; then