[llvm] [clang] [clang-tools-extra] [Clang] Fix linker error for function multiversioning (PR #71706)

[Tom Honermann via cfe-commits]

tahonermann wrote:

@elizabethandrews, PR #73688 seeks to enable ifunc support for Mach-o targets like Darwin. Collaboration might be required to avoid merge conflicts and/or build bot breakage depending on when changes land.

https://github.com/llvm/llvm-project/pull/71706