What is the recommended way to implement a py_binary that writes output(s) to $BINDIR?

[nicholasjng]

Hello Bazel friends, my question is in the title.

The project+PR I'm referencing is nicholasjng/nanobind-bazel#35.

tl,dr: I have a Python script that takes in an .so file, which Bazel also produces in a preceding build step. When I pass that .so file (or rather, its rlocationpath) to the script, it generates a Python stub (.pyi) and optionally a typing marker file, which I intend to put into $BINDIR, because that's where my setuptools extension looks when copying build artifacts from Bazel into the generated wheel.

My question is: Is this a sound approach? I was able to obtain $BINDIR easily from the Python script's location by walking up the path on Unix (because runfiles dirs are contained in / symlinked into the bindir), but it seems that does not work on Windows. So I wanted to get a second opinion on whether this makes sense.

NB: I did not want to use a genrule since that would also have caused problems with Windows compatibility as I understand it (on Windows systems that don't have Bash for instance).

Thanks in advance!