image_signing: Activate file hash cache for watchlist service for signed builds.

This follows the logic introduced in crrev.com/i/2523754

BUG=b:148229706
TEST= ./sign_official_build.sh usb source_image \
          ~/trunk/src/platform/vboot_reference/tests/devkeys out_image
BRANCH=None

Cq-Depend: chrome-internal:3022044
Signed-off-by: Yury Khmel <khmel@google.com>
Change-Id: I5398a9ea2984f0be11cb512f845507309d5f8f8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2210771
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed