cache macos python installation pkg when possible

[trim21]

Description

I'm running cibuildwheel==2.21.3 under macos and windows, I find python on windows is located at C:\Users\runneradmin\AppData\Local\pypa\cibuildwheel\Cache which is inside cibuildwheel cache dir, so it takes 0.00s to install.

But in macos, some python get download every times, for example, cp310 and cp313t take about 40s.

hoping macos python get cached too

Build log

https://github.com/trim21/bencode-py/actions/runs/11825663392/job/32949967762?pr=116

CI config

No response

[mayeut]

macOS uses official python.org installers that requires proper installation in /Library/Frameworks/Python.framework or /Library/Frameworks/PythonT.framework.
It's a 2 steps setup:

• first: download the installer
• second: install CPython

We can't cache the proper installation thus only the download step could be cached which is probably not worth doing.
https://github.com/mayeut/cibuildwheel/actions/runs/12221740312/usage shows only a small timing noise when installers are cached.