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

[via cfe-commits]

dyung wrote:

> > I'll try it and let you know. Give me about an hour or so.
> 
> Awesome! But no huge rush, mostly just hoping this happens to dodge whatever has been tripping up things here.

Sorry for the delay, but the failures still seem to be present. :( (The tests are still running, but the amount of output being generated is slowing things down).

Just a heads up, we are probably going to be upgrading our internal machines and upstream bot to a later build of VS2019 to avoid this issue. I'm validating a newer build today and if all goes well, I am going to try and get it deployed on Friday.

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