fix: support debian multiarch with local toolchains

[rickeylev]

Apparently, there is a "multiarch" style of Python installations, where the shared
libraries can be in a sub-directory. The best docs I could find about this are
https://wiki.debian.org/Python/MultiArch.

To fix, looking at the MULTIARCH sysconfig var tells what subdirectory, if any
should be looked in.

Along the way, fix a changelog issue reference url.

Fixes #3099

[rickeylev]

cc @ekeranen this is slightly different than your patch -- it symlinks origin -> lib/{multiarch_dirname}/{libname}. In your original patch, the second symlink call could overwrite the first.

Hrm, though -- maybe that is wrong? because the libs will be in a sub-dir? Which...all the libpython* stuff probably wants to be in the same dir. But idk if both the regular and multiarch locations could exist? If they do, then what?

Looking at my local system, /usr/bin/python's MULTIARCH does return a value, however, LIBDIR is already pointing there. This is py 3.12. Is py3.8 doing some older behavior?

[ekeranen]

What about implementing this only as a fallback?

if origin.exists: 
    ...
elif origin_multiarch.exists:
   # ... this python installation doesn't set LIBDIR correctly. Fallback to LIBDIR/MULTIARCH. 
   ...

[ekeranen]

LGTM, thanks!

[rickeylev]

yeah, good idea. done.