[clang] [llvm] [WebAssembly] Implement %llvm.thread.pointer intrinsic. NFC (PR #117817)

[Sam Clegg via cfe-commits]

sbc100 wrote:

> > Generally LGTM; maybe we also want to add a test for `__builtin_thread_pointer` to clang/test/CodeGen/builtins-wasm.c
> 
> I only see that testing in clang/test/CodeGen/builtins-arm64.c, most platforms don't seem to test this.

Done!

https://github.com/llvm/llvm-project/pull/117817