Enable rustbot in rustc_codegen_cranelift&rustc_codegen_gcc

[Urgau]

This is going to be useful for enabling [no-mentions] and [issue-links] in both repository.

Which we should anyway to before enabling them in rust-lang/rust as otherwise subtree sync risk being flagged with warnings.

cc @bjorn3 @GuillaumeGomez @antoyo

[Kobzol]

I think that adding triagebot.toml is the main thing, this just adds write access to the triagebot account, but that shouldn't be needed for these checks (it's a good idea regardless though, to track that we use rustbot there).

[github-actions]

Dry-run check results

[WARN  sync_team] sync-team is running in dry mode, no changes will be applied.
[INFO  sync_team] synchronizing github
[INFO  sync_team] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/rustc_codegen_cranelift':
      Permission Changes:
        Giving user 'rustbot' write permission
    📝 Editing repo 'rust-lang/rustc_codegen_gcc':
      Permission Changes:
        Giving user 'rustbot' write permission

[antoyo]

LGTM

[tgross35]

I think that adding triagebot.toml is the main thing, this just adds write access to the triagebot account, but that shouldn't be needed for these checks (it's a good idea regardless though, to track that we use rustbot there).

Write access meaning to post comments, or to write to the repo? I can't think of any time it does the latter.

[Kobzol]

I think that anyone can post comments, write access means merging PRs and pushing commits.

[Urgau]

Doesn't it also allow editing comments, hiding comments, ...? Both are required for these two triagebot features.

[Kobzol]

Good point! I guess it could hide its own comments, but definitely couldn't edit PR descriptions without the write permission.