I note that Mozilla’s bugzilla supports login with github. E.g. see the “Sign in with Github” button on:
https://bugzilla.mozilla.org/enter_bug.cgi
Code looks to be at:
https://github.com/mozilla-bteam/bmo/tree/master/extensions/GitHubAuth
Although it seems to have required some set of changes outside that dir, too. E.g.:
https://github.com/mozilla-bteam/bmo/commit/534fc2123e40b7517aeaffd709faf72af97ac3b8
…and there’s presumably others too.
I must say, it’s really quite unfortunate that the bugzilla that bugzilla uses for its bugs has diverged so far from upstream bugzilla. GithubAuth seems like it should be a plugin that’s shipped with bugzilla upstream, not something that’s private to b.m.o.
But, if someone’s feeling adventurous, it might be possible to integrate that extension into llvm’s bugzilla. Maybe.