[Python] `python -m build` can't find numpy include files when running in cibuildwheel

I'm building a python module that contains a cython file which uses numpy. In some environments python -m build works as is; in other environments I need to set C_INCLUDE_PATH=`python -c "import numpy; print(numpy.get_include())"` beforehand.

But when I type cibuildwheel, I always get fatal error: numpy/arrayobject.h: No such file or directory. I can't figure out how I can help it find these files.

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