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

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov approved this pull request.

LGTM, Thanks.

The changes are a strict improvement.

Pre-existing problem, but it sure looks iffy to me that these data structures are global, not attached to any context.

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