mac: Sign app_mode_loader [badly]

We can't sign the app_mode_loader bundle because it's altered at runtime
as new app mode loader stubs are created. We can sign just the
executable. The resulting executable won't validate in its bundle
normally, and spctl won't like it, but it can be verified with
--ignore-resources, or in isolation from its bundle.

BUG=550972

Review URL: https://codereview.chromium.org/1486863003

Cr-Commit-Position: refs/heads/master@{#363070}
1 file changed