macOS | Universal builds

[carlosperate]

Once Mu moves to the upcoming PyQt5 release with macOS Arm support and/or PyQt6, there is some work that might be needed if we wanted to be able to release a Universal installer.

• Looks like pip install/pip download might favour the architecture of the invoking machine instead of universal wheels
  • macOS apps aren't portable across x86_64/M1 unless all binary wheels are universal2 beeware/briefcase#1217
  • If we are lucky, maybe the current Mu dependencies only offer universal wheels (some projects publish universal, x86, and arm64), but we'll have to check and we'd still be always at a risk of any dependency changing this
• There might not be universal releases of the standalone Python builds yet
  • Suggestion: provide universal binaries for macOS indygreg/python-build-standalone#140