Speed up publishing already signed releases.

Triggering sign-mac on publication is just a safety as the normal
workflows will automatically attempt to sign the releases, which will
succeed almost all of the time. It doesn't have the retries of the
release recipe, though, so we still need this safety. However, we can
speed up the common case with a quick check.

Fixes: b/326228827
Change-Id: I465497874ee2f84c8528b8cf6a735edcf8656191
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/353480
Commit-Queue: Jonas Termansen <sortie@google.com>
Reviewed-by: William Hesse <whesse@google.com>
3 files changed