- Issue #15484: Fix _PYTHON_PROJECT_BASE for srcdir != builddir builds;   use _PYTHON_PROJECT_BASE in distutils/sysconfig.py.
- Issue #15484: Fix _PYTHON_PROJECT_BASE for srcdir != builddir builds;
  use _PYTHON_PROJECT_BASE in distutils/sysconfig.py.

pypa/setuptools,pypa/setuptools,pypa/setuptools