[llvm] IR: Introduce "thread-model" module flag (PR #222768)

[Yonah Goldberg via llvm-commits]

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

I don't see any issues with moving thread-model to module metadata, I haven't been part of the general discussion to do this for all target options from https://discourse.llvm.org/t/synchronizing-lto-code-generation-configuration-between-clang-and-lld-dtlto/91276.

Is there a particular reason you added gonzalo and I? It doesn't look like we use this at all.

https://github.com/llvm/llvm-project/pull/222768