[cbuild] Add bugs link to the Gerrit message

Change-Id: Ib25144825c04a93a03b80297f91e048d09a8af57
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/176261
Reviewed-by: William Hesse <whesse@google.com>
Commit-Queue: Alexander Thomas <athom@google.com>
2 files changed