lal python modules go to /usr/local/lib/python3.11 - Debian 12 Bookworm

Description of problem

Already reported in #542 (closed) for Ubuntu 22.04; the same issue now also shows up with Debian 12 Bookworm: Python modules get installed into /usr/local/lib/ instead of /usr/lib.

This is a general problem affecting all lalsuite parts.

Steps to reproduce

Follow LAL's debían/rules, search for antenna.py etc

Suggested solutions

What I did: In the definitions of purelib and platlib, add a scheme deb_system with a fallback (try/except KeyError) to the "old" style. Patches have been added in the past (up to lal 7.2.4) but those only modified configure (in changing places) and didn't address the underlying problem. More general solution: Using more modern auto*tools and/or building the tarball on a Debian system may provide a stable solution.