Add GitHub Action for checking free-threaded build

[corona10]

Currently, nogil build has been added to buildbot, but it is inconvenient to check whether it is working properly in the PR stage.
So I would like to suggest: Putting a CI that checks nogil builds in Github Action.

This will satisfy the following conditions:

• It will only run against the main branch
• It will check only the build itself and does not run unittests
• (Optional) Even if it fails, it does not fail and does not interfere with other PRs.
  (e.g gh-263: Run Python 3.12 task as the experimental task pyperformance#274)

If this happens, it will be very helpful in reviewing nogil-related PRs.

Linked PRs

• gh-111062: Add nogil build test on GitHub Actions #111060
• [WIP] gh-111062: Add free-threaded CI for Windows(x64) #111437
• GH-111062: Apply reusable workflow for the Linux CI #111440
• gh-111062: Separate macOS build into a reusable workflow #111444
• gh-111062: Separate linux build into a reusable workflow #111446
• gh-111062: Build both default and free-threaded on macOS #111449
• gh-111062: Reusable Ubuntu build that supports free-threaded mode as the conditional CI #111452
• gh-111062: Reusable Windows build that supports free-threaded mode as the conditional CI #111493
• gh-111062: Update name of reusable workflows for Ubuntu / macOS #111494
• gh-111062 CI: Update skip lists for resuable workflows #111521
• gh-111062: CI: Rename reusable-build-[X].yml to reusable-[X].yml #111552
• [3.12] gh-111062: CI: Move OS test jobs to reusable workflows #111568
• [3.11] gh-111062: CI: Move OS test jobs to reusable workflows #111570

[corona10]

As I shared on the discord, I will proceed this issue during the PyCon APAC sprint :)

[corona10]

We are going to set up the CI based on the reusable workflow that @hugovk suggested.
And CIs will be triggered only if the topic-free-threaded is attached.
I will separate it into multiple tasks so that more people can participate in this issue.

• Add topic-free-threaded label
• Add Linux CI based on reusable workflow: @NCLI
• Add macOS CI based on reusable workflow: @dimaqq
• Add Windows CI based on reusable workflow: @jota12x & @corona10

[hugovk]

Please also open an issue about creating a new label: https://github.com/python/core-workflow/issues/new/choose

And see the end of the SC announcement:

We want to avoid negatives in terms and flags and such, so we won’t get into double-negative terrain (like we do when we talk about ‘non no-GIL’). We’d like a positive, clear term to talk about the no-GIL build, and we’re suggesting ‘free-threaded’. (Relatedly, that’s why the build mode/ABI letter is ‘t’ and not ‘n’; that change was already made.)

https://discuss.python.org/t/pep-703-making-the-global-interpreter-lock-optional-in-cpython-acceptance/37075?u=hugovk

So perhaps topic-free-threaded is more appropriate.

[dimaqq]

Taking MacOS for the sprint

[NCLI]

I am taking Linux

[corona10]

Good example: #110794 (comment)