fix(dracut.sh): Ensure hardlink deduplication is reproducible

[cjriches]

By default, hardlink will only deduplicate files with identical mtimes, down to one-second granularity. If a dracut module rapidly generates multiple identical files, it is completely up to chance as to whether their mtimes cross a second boundary or not, and thus whether they get deduplicated or not. This results in non-reproducible output.

Perform timestamp clamping before invoking hardlink if a reproducible build is requested.

Checklist

• I have tested it locally
• I have reviewed and updated any documentation if relevant
• I am providing new code and test(s) for it

[cjriches]

There's a few open questions / alternative approaches here:

• Doing this mtime clamping will also result in more files getting more consistently deduplicated, so it potentially has benefits for everyone - perhaps we should do it unconditionally regardless of --reproducible?
• We could also avoid touching mtimes and just run hardlink -t to deduplicate regardless of mtime match, but there's a small chance this breaks someone who was relying on identical files having different mtimes. The -t option also isn't present in all distros (e.g. it's in RHEL9 but not RHEL8).

[cjriches]

Linked RHEL bug ticket: https://issues.redhat.com/browse/RHEL-101901

[aafeijoo-suse]

Thanks for fixing this hidden issue.

This repo is dead, could you please resubmit this to https://github.com/dracut-ng/dracut-ng?

[cjriches]

Thanks for fixing this hidden issue.

This repo is dead, could you please resubmit this to https://github.com/dracut-ng/dracut-ng?

Thanks, have done: dracut-ng/dracut#1429

If you have the power to do so, I would suggest updating the README of this repo and marking it as archived, so that future contributors don't make the same mistake.