Harden our code signing on macOS for ESR 78
While legacy/trac#32506 (moved) might be not doable during our transition to ESR 78 we might be able to pick up some improvements nevertheless, see:
https://hg.mozilla.org/releases/mozilla-beta/rev/497690887467ccf0709d71fdb1b20d0647388df9
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information