ci(seed-build): checkout codebase based on ref

[miooochi]

Background

Check out to codebase based on a given github.sha. This is necessary when we do future releases.

Quoted from https://github.com/actions/checkout

   # The branch, tag or SHA to checkout. When checking out the repository that
   # triggered a workflow, this defaults to the reference or SHA for that event.
   # Otherwise, uses the default branch.
   ref: ''

Checklist

• The Pull Request has been fully tested
• There's an entry in the CHANGELOGS
• There is a user-facing docs PR against https://github.com/daeuniverse/dae

Full changelogs

• ci(seed-build): checkout codebase based on ref

Issue reference

NA

Test Result

NA