.github: Add image change reports to CI workflow

[krnowak]

/build-image

[pothos]

Thanks, did you also start a Jenkins job already?

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/5800173048

[krnowak]

Thanks, did you also start a Jenkins job already?

Yep, and worked from the beginning, contrary to Github. :/ Here: http://jenkins.infra.kinvolk.io:8080/job/container/job/packages_all_arches/2264/cldsv/

[krnowak]

Reports are generated also on github, you can download them from https://github.com/flatcar/scripts/actions/runs/5784886439?pr=1046 (look for image-changes-reports). Jenkins still works - http://jenkins.infra.kinvolk.io:8080/job/container/job/packages_all_arches/2264/cldsv (note that the reports generated by Jenkins is different than a github one, because Jenkins was running on an older checkout of the branch).