CI: Use ImageOS (ubuntu24) instead of runner.os (Linux) in cache keys

[hugovk]

Problem

In #129834 we recently switched the ubuntu-24.04-arm runners to ubuntu-22.04-arm.

However, the CI jobs consistently broken due to an unknown GCC option:

• https://github.com/python/cpython/actions/runs/13214375613/job/36891873483?pr=129779

After clearing the config caches, a re-run passed:

• https://github.com/python/cpython/actions/runs/13214375613/job/36892182753?pr=129779

This was the cache key for "Restore config.cache" is:

key: ${{ github.job }}-${{ runner.os }}-${{ env.IMAGE_VERSION }}-${{ inputs.config_hash }}

Which evaluates to build_ubuntu_reusable-Linux-0.0.10-9cf14f6717fb4cec718ff086229088aa00b4e898b87da1d8f14119ec638f68e7 for both runners.

That is because runner.os is Linux and env.IMAGE_VERSION is 0.0.10 for both.

So they both used the same cache.

Fix

env.IMAGE_VERSION comes from $ImageVersion, and there's also a $ImageOS which gives ubuntu22 or ubuntu24.

This will give us a fresh cache when we next change the OS version.

[hugovk]

This was set but not used in this job.

[hugovk]

This wasn't being set in this job, so env.IMAGE_VERSION was evaluating as an empty string in the keys below.

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @hugovk, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3d7a141c2f235b70dd6c2d64308022c4b77df131 3.13

[miss-islington-app]

Sorry, @hugovk, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3d7a141c2f235b70dd6c2d64308022c4b77df131 3.12

[bedevere-app]

GH-130222 is a backport of this pull request to the 3.13 branch.

[bedevere-app]

GH-130226 is a backport of this pull request to the 3.12 branch.

[hugovk]

And let's backport to 3.9-3.11 because they're still using ubuntu-20.04 which will be fully unsupported by 2025-04-01, so this fix is needed before we upgrade those:

#122566 (comment)

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @hugovk, I could not cleanly backport this to 3.10 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3d7a141c2f235b70dd6c2d64308022c4b77df131 3.10

[miss-islington-app]

Sorry, @hugovk, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3d7a141c2f235b70dd6c2d64308022c4b77df131 3.11

[miss-islington-app]

Sorry, @hugovk, I could not cleanly backport this to 3.9 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 3d7a141c2f235b70dd6c2d64308022c4b77df131 3.9

[bedevere-app]

GH-130252 is a backport of this pull request to the 3.11 branch.

[hugovk]

And let's backport to 3.9-3.11 because they're still using ubuntu-20.04 which will be fully unsupported by 2025-04-01, so this fix is needed before we upgrade those:

#122566 (comment)

3.9 and 3.10 don't have these cache keys so don't need this backport.