Feature or enhancement

tools/wasm/wasm_build.py does not have an easy way to build submodules.

Pitch

PKG_CONFIG_PATH could be used to support say things like https://github.com/hoodmane/libffi-emscripten.

I propose adding this to the wasm_build.py to support custom package configs.

Previous discussion

https://discuss.python.org/t/get-ctypes-working-in-emscripten-build/18466/2