[clang] [Clang] Add __builtin_bswapg (PR #162433)

[via cfe-commits]

clingfei wrote:

> > I accidentally added a large number of unintended reviewers. Could you help me remove them?
> 
> I believe I've got it back to the right set :D

Thanks! 

> How did you update your branch? (My suspicion is that something about that caused GitHub to suggest every person involved in all the merged PRs)

I performed a local rebase onto the main branch and pushed to my own branch.


https://github.com/llvm/llvm-project/pull/162433