MinGW is currently failing in main - https://github.com/python-pillow/Pillow/actions/runs/4861154081

https://www.msys2.org/docs/python/ states

setuptools >= 60.0 is currently incompatible with MSYS2. You can set export SETUPTOOLS_USE_DISTUTILS=stdlib to work around the issue. We are currently working on restoring compatibility.

Adding in SETUPTOOLS_USE_DISTUTILS="stdlib" fixes the problem.