Per discussion in https://github.com/pypa/cibuildwheel/pull/1169, the default installer used for cp38 is an Intel installer.
It makes sense to skip testing arm64 wheels in this case.
However, if the user choose to manually install the universal2 CPython version, then, tests shall be run on arm64.
This allows users that either target 11.0+ on intel, universal2 or only build for arm64 to get the arm64 wheel tested on AppleSilicon.
Gives us a little more flex for the Cirrus build. I've set these to the maximum because we already use pytest-timeout to catch stalled tests, so there's little need to be conservative. MacOS ARM and aarch64 linux are currently running at 5 and 20 minutes respectively, so no need to increase their limits.
See https://github.com/pypa/cibuildwheel/runs/8321188914 for an example timeout on Linux x86
Joe Rickerby