[clang] [WebAssembly,clang] Add __builtin_wasm_test_function_pointer_signature (PR #150201)

[Derek Schuff via cfe-commits]

dschuff wrote:

This change looks fine.
Regarding nontrapping call, In general I think we probably shouldn't have clang builtins for functionality that can be implemented in code on top of existing builtins. Builtins are basically language extensions (but often without the extensive vetting that language design usually includes), and as part of a low-level platform, they are hard to change. Also if we start with something minimal it's easier to push functionality down the platform stack in the future (e.g. by adding the builtin later).

https://github.com/llvm/llvm-project/pull/150201