Patch #103279: sysconfig.py always looks for versions of files in sys.prefix + 'config/Makefile'. When building Python for the first time, these files aren't there, so the files from the build tree have to be used instead; this file adds an entry point for specifying that the build tree files should be used.  (Perhaps 'set_python_build' should should be preceded with an underscore?)
Patch #103279: sysconfig.py always looks for versions of files in
sys.prefix + 'config/Makefile'. When building Python for the first
time, these files aren't there, so the files from the build tree have
to be used instead; this file adds an entry point for specifying that
the build tree files should be used.  (Perhaps 'set_python_build' should
should be preceded with an underscore?)

pypa/setuptools,pypa/setuptools,pypa/setuptools