[clang] [compiler-rt] [Clang][PGO] Fix profile function visibility bug (PR #127257)

[David Tellenbach via llvm-commits]

dtellenbach wrote:

@EthanLuisMcDonough I think your patch effectively introduces a dependency on libc because `__llvm_write_custom_profile` has `__attribute__((uses))`` but calls e.g. `atoi` through `setupIOBuffer`.

In compiler-rt it's not safe to make that assumption because it potentially breaks embedded platforms. IMO it's also bad practice to force used symbols into a static archive. Would you please take another look and at least make the functionality dependent on offloading or something similar?

Thanks a lot!

https://github.com/llvm/llvm-project/pull/127257