py39-matplotlib fails on lion. py39-matplotlib is using libstdc++ (this installation is configured to use libc++)

[RobK88]

py39-matplotlib fails on lion (10.7.5).

py39-matplotlib is using libstdc++ (this installation is configured to use libc++)

Why is py39-matplotlib usng libstc++? Macports switched over to libc++ a long time ago!

bash-3.2$ sudo port clean py39-matplotlib
--->  Cleaning py39-matplotlib
bash-3.2$ sudo port -v upgrade  py39-matplotlib
--->  Computing dependencies for py39-zopfli.
--->  Fetching distfiles for py39-zopfli
--->  Verifying checksums for py39-zopfli
--->  Checksumming zopfli-0.2.1.zip
--->  Extracting py39-zopfli
--->  Extracting zopfli-0.2.1.zip
Executing:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_python_py-zopfli/py39-zopfli/work" && /usr/bin/unzip -q '/opt/local/var/macports/distfiles/py-zopfli/zopfli-0.2.1.zip' -d /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_python_py-zopfli/py39-zopfli/work 
--->  Configuring py39-zopfli
--->  Building py39-zopfli
Executing:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_python_py-zopfli/py39-zopfli/work/zopfli-0.2.1" && /opt/local/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9 -m build --wheel --no-isolation --outdir /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_python_py-zopfli/py39-zopfli/work 
/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/config/setupcfg.py:463: SetuptoolsDeprecationWarning: The license_file parameter is deprecated, use license_files instead.
  warnings.warn(msg, warning_class)
/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/config/setupcfg.py:463: SetuptoolsDeprecationWarning: The license_file parameter is deprecated, use license_files instead.
  warnings.warn(msg, warning_class)
running bdist_wheel
running build
running build_py
creating build
creating build/lib.macosx-10.7-x86_64-cpython-39
creating build/lib.macosx-10.7-x86_64-cpython-39/zopfli

etc
etc

--->  Cleaning py39-matplotlib
--->  Removing work directory for py39-matplotlib
--->  Scanning binaries for linking errors
--->  No broken files found.                             
py39-zopfli is using libstdc++ (this installation is configured to use libc++)
py39-matplotlib is using libstdc++ (this installation is configured to use libc++)
--->  Found 2 broken ports, determining rebuild order
You can always run 'port rev-upgrade' again to fix errors.
The following ports will be rebuilt:
 py39-zopfli @0.2.1
 py39-matplotlib @3.5.2+cairo+webagg
Continue? [Y/n]: