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

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

@DanielKristofKiss From your response, I gather you want AArch64 to align with the other targets, but additional changes are required to make that work?

In the interest of keeping things moving, how do you want to stage this?  Would it make sense to land this as-is?  Rhen you can remove the aarch64-specific codepath along with whatever other changes are necessary.

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