[llvm] [BOLT] Fix unused variable warning (PR #93323)

[Amir Ayupov via llvm-commits]

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

Looks good, but please do the following before merging:
- add '[NFC]' to title (check other BOLT commits for examples)
- remove file path from commit message

https://github.com/llvm/llvm-project/pull/93323