Try to resolve build failures by switching back to CPython's distutils instead...

Try to resolve build failures by switching back to CPython's distutils instead of using the one in setuptools 0.60.

See https://github.com/pypa/setuptools/pull/2896
See https://github.com/cython/cython/pull/4510

.github/workflows/ci.yml

@@ -191,6 +191,9 @@ jobs:
       BACKEND: ${{ matrix.backend }}
       OS_NAME: ${{ matrix.os }}
       PYTHON_VERSION: ${{ matrix.python-version }}
+      # Use CPython's distutils instead of setuptools's copy.
+      # See https://github.com/pypa/setuptools/pull/2896
+      SETUPTOOLS_USE_DISTUTILS: local
       GCC_VERSION: 8
       USE_CCACHE: 1
       CCACHE_SLOPPINESS: "pch_defines,time_macros"

Makefile

@@ -90,6 +90,7 @@ wheel_%: dist/$(PACKAGENAME)-$(VERSION).tar.gz
 		-e CFLAGS="$(MANYLINUX_CFLAGS)" \
 		-e LDFLAGS="$(MANYLINUX_LDFLAGS) -fPIC" \
 		-e WHEELHOUSE=wheelhouse$(subst wheel_musllinux,,$(subst wheel_manylinux,,$@)) \
+	    -e SETUPTOOLS_USE_DISTUTILS=local \
 		quay.io/pypa/$(subst wheel_,,$@) \
 		bash -c '\
 			rm -fr /opt/python/*pypy* ; \