[clang] Patch series to reapply #118734 and substantially improve it (PR #120534)

[via cfe-commits]

dyung wrote:

> @dyung -- Could you try out https://github.com/chandlerc/llvm-project/tree/shard-loongarch and see if that works?
> 
> Notably, it includes one additional patch on top of this series: [chandlerc at 2d59328](https://github.com/chandlerc/llvm-project/commit/2d593288dc18c55307779ae82a18d024761356ad)
> 
> This won't be enough to fully resolve the issue, but if the LoongArch errors go away with this patch, then it gives me a strong theory about what is still going wrong and I can likely find a workaround for the rest as well.

Sorry for the delay, here are the results of running the branch shard-loongarch. Main takeaway is that the loongarch failures seem to have been fixed with the patch at the HEAD of that branch.

I have uploaded the test logfile here (another 300MB file when expanded):
https://www.dropbox.com/scl/fi/8v8toveo8h45c4iuwjgo8/log_test.f6426abc224b140bfb3b6fdc45443bc4e16057aa.zip?rlkey=6rj3vygil705ddd63vk4ykqdl&dl=0

https://github.com/llvm/llvm-project/pull/120534