Several tests register signal handlers with the wrong C signature.

For example:
https://github.com/emscripten-core/posixtestsuite/blob/a5e7ff5f906c9a8f18d70f6472c4055bc311c34d/conformance/interfaces/pthread_spin_lock/3-2.c#L28

I'm not sure how common this is in the wild but it hard to make this work in WebAssembly were we have strong type checking on function signatures.

Start with conformance/interfaces/pthread_spin_lock/3-2.c at line 28 and inspect how the signal handler is declared and registered. Search the test suite for similar registrations, update each affected test to use the required C signature, and run the relevant POSIX tests under WebAssembly to confirm they pass.

Written by the indexing model from the issue text.