[clang] [clang][FMV] Fix crash with cpu_specific attribute. (PR #115762)

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elizabethandrews wrote:

> > > Wouldn't mind it if @Fznamznon took a look though, IIRC, she did a bunch of work with cpu_specific/cpu_dispatch.
> > 
> > 
> > I don't think I did. I'm not familiar with this area to provide any opinion.
> 
> Ah, hrmph... maybe it was @elizabethandrews who did a bunch of multiversioning stuff lately?

I briefly worked on `target_clones` about a year back. I am not very familiar with requirements for `cpu_specific`. Having said I (naively) think that this PR looks ok since it seems like it just reverts behavior of `cpu_specific` to whatever it was before https://github.com/llvm/llvm-project/commit/a2d309912a2863dfe7286ffde67b968e8c720b07#diff-e724febedab9c1a2832bf2056d208ff02ddcb2e6f90b5a653afc9b19ac78a5d7 ? 

https://github.com/llvm/llvm-project/pull/115762