[llvm] [Attributor] Check callback broker argument aliases correctly (PR #218672)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM, though I found the terminology in your PR description a bit confusing (I don't think I've seen "broker" used in the context of abstract call-sites before?)

https://github.com/llvm/llvm-project/pull/218672