fix: Handle buildx output with BUILDX_NO_DEFAULT_ATTESTATIONS=1

[tobni]

Related reading as to why attestations can be disabled by users: aws/aws-cdk#30258, https://stackoverflow.com/questions/77207485/why-are-there-extra-untagged-images-in-amazon-ecr-after-doing-docker-push

In short, upstream tooling is not really ready for buildx + docker desktop default outputs, and when disabling these we get a stdout which current pants parsing code was not ready for.

Fixes #21729

[huonw]

Thanks for this

[WorkerPants]

I tried to automatically cherry-pick this change back to each relevant milestone, so that it is available in those older releases of Pants.

❌ 2.22.x

I was unable to cherry-pick this PR to 2.22.x, likely due to merge-conflicts.

Steps to Cherry-Pick locally

To resolve:

1. (Ensure your git working directory is clean)
2. Run the following script to reproduce the merge-conflicts:

   git fetch https://github.com/pantsbuild/pants main \
     && git fetch https://github.com/pantsbuild/pants 2.22.x \
     && git checkout -b cherry-pick-21735-to-2.22.x FETCH_HEAD \
     && git cherry-pick b0c8d8e0db38d3f63cbd633803a5a3a7d09231c5

3. Fix the merge conflicts and commit the changes
4. Run build-support/cherry_pick/make_pr.sh "21735" "2.22.x"

Please note that I cannot re-run CI if a job fails. Please work with your PR approver(s) to re-run CI if necessary.

✔️ 2.23.x

Successfully opened #21738.

✔️ 2.24.x

Successfully opened #21737.

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When you're done manually cherry-picking, please remove the needs-cherrypick label on this PR.

Thanks again for your contributions!

🤖 Beep Boop here's my run link