[clang] Patch series to reapply #119638 and substantially improve it (PR #120534)

[Chandler Carruth via cfe-commits]

chandlerc wrote:

@dyung - I believe this PR may be a credible path to address the issues hit with your MSVC builders, would appreciate any help testing it in advance if possible.

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