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

[Hood Chatham via cfe-commits]

hoodmane wrote:

Well it would also be possible to make success the return value, and make the first argument a `void* result`. This would be a more normal API, but it has the disadvantage that it would never be able to work with functions that return reference types. Maybe that isn't that big of a deal I suppose?

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