[clang] [Clang][InstrProf] Allow absolute path in fun.list of -fprofile-list= (PR #67519)

[Henrik G. Olsson via cfe-commits]

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

Please update `clang/test/CodeGen/profile-filter.c` with some cases that exercise the new code path.

https://github.com/llvm/llvm-project/pull/67519