[llvm] [InlineCost] Use a const reference (NFC) (PR #95687)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

See the comment directly above. The copy here is needed for the legacy pass manager. It looks like we still support AlwaysInliner for the legacy PM.

https://github.com/llvm/llvm-project/pull/95687