gh-121487: Fix deprecation warning for ATOMIC_VAR_INIT in mimalloc

[cdce8p]

Pull in upstream changes to fix deprecation warning with ATOMIC_VAR_INITin mimalloc.

• microsoft/mimalloc@36ee5f9
• microsoft/mimalloc@1325ee6

• Issue: Deprecation warning for ATOMIC_VAR_INIT in mimalloc #121487

[colesbury]

Thanks!

[miss-islington-app]

Thanks @cdce8p for the PR, and @colesbury for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-121504 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Fedora Stable Clang Installed 3.x has failed when building commit 31873be.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/350/builds/6261) and take a look at the build logs.
4. Check if the failure is related to this commit (31873be) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/350/builds/6261

Summary of the results of the build (if available):

Click to see traceback logs

fatal: unable to access 'https://github.com/python/cpython.git/': Could not resolve host: github.com

chmod: cannot access 'target/': No such file or directory

make: *** No rule to make target 'distclean'.  Stop.