Python@3.9 fails to install on ARM Big Sur

[lewis262626]

Python expects a float for the MACOSX_DEPLOYMENT_TARGET compiler option,
if it is an integer it fails to install.

For some reason on Arm64 Big Sur the call to MacOS.version returns 11.

This fixes Homebrew/brew#9329

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

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[citelao]

I can confirm that python@3.9 (as part of brew install -s imagemagick@6) installs correctly when I made this change manually to my python@3.9.rb formula.

[jguerin]

Confirmed that this helped me finish installing ninja

[fxcoudert]

For some reason on Arm64 Big Sur the call to MacOS.version returns 11

Because MacOS.version returns the major version number, which is 11

Python expects a float for the MACOSX_DEPLOYMENT_TARGET compiler option

$ MACOSX_DEPLOYMENT_TARGET=11 clang a.c && echo $?
0

11 is a valid value for MACOSX_DEPLOYMENT_TARGET. This bug needs to be reported to Python and fixed there. If they have a patch for it, we can use that patch here.

[d12frosted]

I confirm that this issue affects not only M1, but even old macs. Applying the change locally fixes the problem. Thank you @lewisrobbins for this!

Since python is a dependency for other packages, I think this issue hits many users. Not sure where it should be fixed, but would be lovely to avoid the need of manual patching 😸

[guillochon]

I created a bug report here on the Python project, hopefully that's the right place to put it: https://bugs.python.org/issue42505

[fxcoudert]

I've reported it to Python: https://bugs.python.org/issue42504

[guillochon]

I closed my issue and linked back to yours since we created them at almost the same time. 😄

[fxcoudert]

And opened a pull request with a fix: python/cpython#23556

[fxcoudert]

Upstream patch being added: #65953