[llvm] [BOLT] Improve regexp in link_fdata.py (PR #152694)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Thanks Gergely.

Please allow 1-2 days in case there are any objections.

https://github.com/llvm/llvm-project/pull/152694