common: Add cr50 into factory shim

Only mask the two largest directories (/opt/google/chrome and
/opt/google/containers) in factory shim image, so that cr50 is included
in factory shim.

BUG=b:118821734
TEST=build factory shim and check there is /opt/google/cr50

Change-Id: I4a571b5a33b3549d37f26e01b468c5e7ebea43b0
Reviewed-on: https://chromium-review.googlesource.com/1314231
Commit-Ready: Cheng-Han Yang <chenghan@chromium.org>
Tested-by: Cheng-Han Yang <chenghan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
(cherry picked from commit c924c2c400cff1aee041b776c22908cadb443604)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1985644
Reviewed-by: Cheng-Han Yang <chenghan@chromium.org>
Commit-Queue: Cheng-Han Yang <chenghan@chromium.org>
diff --git a/common.sh b/common.sh
index 860a431..996db6a 100644
--- a/common.sh
+++ b/common.sh
@@ -489,7 +489,8 @@
 # Mask for factory install shim (build_image factory_install)
 FACTORY_SHIM_INSTALL_MASK="
   ${DEFAULT_INSTALL_MASK}
-  /opt
+  /opt/google/chrome
+  /opt/google/containers
   /usr/lib64/dri
   /usr/lib/dri
   /usr/share/X11