contrib: add a script to build all of the wheels on macOS
This is mostly a translation of `contrib/packaging/build-windows-wheels.bat`,
except the default pythons to build can be inferred from `setup.py` and/or
`pyproject.toml`, and all use the same configuration. All we need to do is
force the building of translation files, tell it to skip pypy wheels, and tell
it to build universal2 wheels instead of for the current architecture.
<item>
<title>{branch|escape}</title>
<link>{urlbase}{url|urlescape}rev/{node|short}</link>
<description><![CDATA[{branch|strip|escape|addbreaks}]]></description>
<pubDate>{date|rfc822date}</pubDate>
</item>