py39-pdm-backend fails to build in Sonoma 14.7.6

[Joshua Root]

> Since a few days ago the py39-pdm-backend package fails to build under
> Sonoma 14.7.6 using Macports 2.10.5 or 2.10.6
>
> :/debug:build system: cd /"/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-pdm-backend/py39-pdm-backend/work/pdm_backend-2.4.4"
> &&
> /opt/local/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9
> -m build --no-isolation --wheel --outdir
> /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-pdm-backend/py39-pdm-backend/work
> :/info:build * Getting build dependencies for wheel... /:/info:build ERROR Missing dependencies: /:/info:build importlib-metadata>=3.6; python_version < "3.10" /
>
The problem is that py39-importlib-metadata is not recording its version 
correctly. I opened a ticket: <https://trac.macports.org/ticket/72425>

- Josh