[clang] [llvm] Singleton hack of fixing static initialisation order fiasco (PR #154541)

[Mircea Trofin via cfe-commits]

mtrofin wrote:

> p.s. The branch is saying it is out of date very frequently. Should I update branch or would it be fine to leave it?

Don't bother, not worth doing until the very end. If you don't have write permissions to the repo, I can help with the merging (to be clear, you maintain authorship, I can just push the button). If I hit any conflicts, I'll let you know.

https://github.com/llvm/llvm-project/pull/154541