Handle renovate version comments in build script

[echoix]

Fixes #

Proposed Changes

1. Consider ARG instructions lines starting with # renovate: as an ARG instruction
2. Consider ARG instructions when separating ARG from FROM instructions.
3. …

Readiness Checklist

Author/Contributor

• Add entry to the CHANGELOG listing the change and linking to the corresponding issue (if appropriate)
• If documentation is needed for this change, has that been included in this pull request

Reviewing Maintainer

• Label as breaking if this is a large fundamental change
• Label as either automation, bug, documentation, enhancement, infrastructure, or performance

[echoix]

I'd like this to be merged before enabling renovate. It will allow to create some PRs adding version comments + build args and seeing them in the on-boarding PR.

[nvuillam]

Let's see :)