AC allows to set runstatedir but looks like python's configure is a bit outdated, it requires to be regenerated.

Upstream autoconf has not had a release in many years. Ubuntu packages a unreleased upstream version that adds runstatedir. Absent a more rigorous process for the regeneration of configure, this change is not useful; it will just get overwritten the next time someone with an older autoconf regenerates it.

When a core developer updates configure.ac, they use their local version of autoconf. It may or may not generate --runstatedir. It doesn't seem common to co-install multiple versions of autoconf, and so we cannot require all core developers to have one specific autoconf version, or a minimum version.

I close the issue. Reopen it or open a new issue if you would like to experiment a different approach.

Fedora always regenerates the configure script from configure.ac. Maybe other Linux distributions do something similar.

The configure script is tracked by Git since it's more convenient for core developers. It's uncommon to update configure.ac, and it avoids a dependency on autoconf to quickly hack CPython.