bpo-43974: Move Py_BUILD_CORE_MODULE into module code (GH-29157) by tiran · Pull Request #29157 · python/cpython

``setup.py`` no longer defines ``Py_BUILD_CORE_MODULE``. Instead every
module defines the macro before ``#include "Python.h"`` unless
``Py_BUILD_CORE_BUILTIN`` is already defined.

``Py_BUILD_CORE_BUILTIN`` is defined for every module that is built by
``Modules/Setup``.

Signed-off-by: Christian Heimes <christian@python.org>

Makefile and makesetup already define ``Py_BUILD_CORE_BUILTIN`` and
include ``Modules/internal`` for us.