Our package build process currently has a significant flaw: we first run setup.py, recording all compilation commands, then we rewrite these compilation commands to invoke emcc and replay them, and then we pray that the cross compiled executables ended up in the right place to go into the wheel. This is not a good strategy because the build script is allowed to implement arbitrary logic, and if it moves, renames, etc any of the output files then we lose track of them. This has repeatedly caused difficulty for us.
However, we also make no particularly significant use of the two pass approach. We can just do the simpler thing: capture the compiler commands as they occur, modify them as needed, and then run the fixed command.
I also added a patch to fix the numpy feature detection for wasm so that we don't have to include _npyconfig.h and config.h, numpy can generate them in the way it would for a native build. I opened a numpy PR that would fix the detection for us upstream:
numpy/numpy#21154
This clears the way for us to switch to using pypa/build (as @henryiii has suggested) by removing our dependence on specific setuptools behavior.
This is on top of #2238.
Gyeongjae Choi