[clang] [llvm] Implement `preserve_none` for 32-bit x86 (PR #150106)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon requested changes to this pull request.

@brandtbucher are you still looking at this? if so please update the patch to trunk latest and address the merge failure

https://github.com/llvm/llvm-project/pull/150106