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

[Mircea Trofin via cfe-commits]

mtrofin wrote:

Please refer to [our guidelines](https://llvm.org/docs/DeveloperPolicy.html#commit-messages) for commit messages. At minimum, explaining what the problem is and any relevant context would help the reviewers.

Similar idea for the referenced issue: giving a description of the problem would help the reader. The Valgrind trace is useful afterwards, as support for what would be claimed as the problem.

(If there's a [discourse](https://discourse.llvm.org/) topic this is in answer to, referencing it would also help)

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