Fix filesystem leak in keg tests
Return early from resolve_any_conflicts for non-symlinks
Handle broken symlinks in resolve_any_conflicts

Fixes #33328.
Less code in begin block
Build `hub` HEAD with Go

The `hub` 2.2.0 branch has been [merged into master](https://github.com/github/hub/pull/641).
HEAD requires Go and a different script to build.
The 1.x stable build should still work before 2.2.0 is officially released.
hub: add 1.12.2 bottle.