Emscripten build with NODERAWFS=1

[thomasballinger]

It might be helpful for tests? being in a more familiar environment? to do an emscripten build that uses the native filesystem, which is possible with NODERAWFS replacing the Emscripten in-memory filesystem. This would get us close to something like node python.js script.py.

FIle permissions don't quite work the same There are some limitations to going through this layer, but it's pretty seamless for the filesystem access that node does provide. This might let folks install the emscripten-compiled version of Python alongside other python builds like pypy.

WASI support seems strategically more important, but this could be a useful foothold.

[emmatyping]

Yeah more broadly we should try building with Emscripten targeting node as that will be easier to test

[emmatyping]

Fixed in python/cpython#30552