bpo-41100: Support macOS 11 and Apple Silicon (GH-22855)

[sjmulder]

Backport of commit 4176193 to 3.9:

---

Co-authored-by: Lawrence D’Anna lawrence_danna@apple.com

• Add support for macOS 11 and Apple Silicon (aka arm64)

  As a side effect of this work use the system copy of libffi on macOS,
  and remove the vendored copy

• Support building on recent versions of macOS while deploying to older
  versions

  This allows building installers on macOS 11 while still supporting
  macOS 10.9.

https://bugs.python.org/issue41100

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[sjmulder]

I haven't done anything with the codebase before so please be gentle. In particular, I don't know if this is the right way to do a backport pull request.

[ned-deily]

Thanks for the interest but we will be back porting this and other changes to 3.9 soon.

[sjmulder]

Did I do it wrong then? Why can't one submit a backport?

[ned-deily]

Did I do it wrong then? Why can't one submit a backport?

The core developer(s) handling the original merge to the master branch is normally responsible for deciding what and where to backport and we have automatic tools to help core developers do the work. At first glance, that's what I thought had happened here but, if not, thank you for doing the backport work yourself. Especially with this feature, there are still some pieces to be added so it's best to follow our normal workflow, although it would be interesting to know if you had to manually modify any pieces to backport properly. The process is described in the developers guide, primarily here.

[sjmulder]

Thanks for explaining! I used a regular git cherry pick, there were only a few things to clean up. After that, I had to make two more changes:

• Fix _decimal: sjmulder@d7080b5
• Adding search paths to find libbz2.tbd and libz.tbd: sjmulder@e77f5da

These were the minimal changes necessary to get the package building in pkgsrc; there may be more work to do. I’ll be looking forward to the proper release.