community/<various>: Fixes to fix mirage

@Bridouz Do these changes to py3-mypy look fine? abuild says it has no arch-specific binaries so I set it to noarch, but maybe there's a good reason it isn't right now? If so, I'd like there to be a comment explaining why.

Fixes #12597 (closed)

Tested and works on a fresh postmarketOS image. Also works in an already-existing Alpine installation.

As for the lint failures, when I remove $builddir the packages don't build because the builddir doesn't get set right.