python3.9 and python3.6 were the only remaining Pythons that are "flatpackaged".
As they are likely to stay around for a while,
it makes no sense to wait this out (like we did with e.g. 3.7 and 3.8).
This (together with similar change in python3.9)
will make all the packaged Pythons packaged in the same way.
Additionally, this also enables the debug build, which was added to CI.
See https://src.fedoraproject.org/rpms/python3.9/c/7a81f94ccc
Assisted-By: Cursor 2.0.38 with gpt-5
