[3.9] bpo-42591: Export missing Py_FrozenMain() symbol (GH-23730) by vstinner · Pull Request #23734 · python/cpython

@vstinner

Export the Py_FrozenMain() function: fix a Python 3.9.0 regression.
Python 3.9 uses -fvisibility=hidden and the function was not exported
explicitly and so not exported.

(cherry picked from commit b5c7b38)