Currently implemented:

• Adds custom wasm binary name support proposed in WebAssembly support #438 (comment), sample usage:

  struct MyExtension;
  
  #[gdextension]
  unsafe impl ExtensionLibrary for MyExtension {
   fn override_wasm_binary() -> Option<&'static str> {
        // Binary name unchanged ("mycrate.wasm") without thread support.
        #[cfg(feature = "nothreads")]
        return None;
  
        // Tell gdext we add a custom suffix to the binary with thread support.
        // Please note that this is not needed if "mycrate.threads.wasm" is used.
        // (You could return `None` as well in that particular case.)
        #[cfg(not(feature = "nothreads"))]
        Some("mycrate-with-threads.wasm")
    }
  }

• Fixes wasm_nothreads compilation by not using compiled out function in async_runtime.rs (regression from Async Signals #1043)

• Fixes wasm_nothreads runtime errors on init due to thread locals being used for panic handling (regression from Panic handling: thread safety; set hook once and not repeatedly #1037)

TODO

Working on these, but feel free to review or merge what's already there.

• Potentially fix the rest of async_runtime to e.g. not use std::thread::current on nothreads builds (might need to be in a separate PR Let's do that in a separate PR (edit: using that function is actually fine, let's keep an eye on it in case anything else could be a problem)
• Automatically detect .threads.wasm when it still uses the crate name to avoid having to use the option introduced above outside atypical cases