Update wasm build to use bigint

[nonameentername]

godot-cpp does not use the same compilation flags for wasm as godot. This change fixes import errors from mismatched function signatures.

Fixes godotengine/godot#96492
Fixes #1553

[raulsntos]

In the main repo I could only find this flag appended to LINKFLAGS:

https://github.com/godotengine/godot/blob/ce8a837aab2568f9cdc41b4b410c478b0cd711fc/platform/web/detect.py#L275-L276

And only when the emscripten version is greater than 3.1.41, or when proxy_to_pthread is enabled.

[nonameentername]

Thanks, I'll update pr to do the same.

[Faless]

Suggested change

	env.Append(CCFLAGS=["-sWASM_BIGINT"])
	env.Append(LINKFLAGS=["-sWASM_BIGINT"])
	env.Append(LINKFLAGS=["-sWASM_BIGINT"])

Since we need to build gdextensions with emscripten => 3.1.62 (better if == 3.1.62) to support gdextensions, we don't need to check the compiler version or proxy_to_pthread (in fact, I think we should remove those conditionals in upstream Godot to, and always require emscripten => 3.1.62).

[adamscott]

@Faless I'll create a PR for this for the main repo.

[dsnopek]

Looks like we're still waiting on the CCFLAGS line to be removed. But once that's done, I think this should be OK to merge!

[Faless]

I've opened #1603 because this can't be delayed much longer, since it breaks all web GDExtensions.