[3.9] gh-97032: avoid test_squeezer crash on macOS buildbots (GH-115508)

[miss-islington]

avoid test_squeezer crash on macOS buildbots
(cherry picked from commit 17a6533)

Co-authored-by: Ned Deily nad@python.org

• Issue: GUI tests: CPython 3.9 CI failure for macOS: macOS 11 (1107) or later required, have instead 11 (1106) ! #97032

[encukou]

!buildbot ARM64 MacOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @encukou for commit 62b8d31 🤖

The command will test the builders whose names match following regular expression: ARM64 MacOS

The builders matched are:

• ARM64 MacOS M1 Refleaks NoGIL PR
• ARM64 MacOS M1 NoGIL PR
• ARM64 macOS PR

[encukou]

PR buildbot failures are unrelated.

@ambv, IMO this is the best way to fix the 3.9 buildbot failures. There's a more robust fix in later branches.
The other approaches considered are:

• change library detection logic, which isn't ideal in source-only security releases
• configuring the buildbot to use Homebrew tkinter -- too much work for a library that isn't really tested anyway

See Pablo's comment for 3.10:

While I understand the fix and the rationale, I have to say that I still find it a bit "hacky" (for the lack of a better term). Given that this is to fix CI in old branches I am fine merging it as it has no user impact, but ideally we should fix this in the build system in main if we detect that we are using an incompatible tkinter .

I any case, I am merging this as I think the proper fix will be more aggressive and we need to have the CI green to avoid hiding other problems. Thanks @encukou and @ned-deily for the PR and the explanation.

In main, the build system prefers pkg-config, and shouldn't pick up Apple's abandoned tk.