build-docker-image: Allow to run locally through a docker agent
Some job using docker cannot easily be built using the host since they require some mount points to happen. Using a docker agent ease such build.
So this mr proposes to update the instruction to be able to reproduce some of those builds:
- build-docker-image
- (ongoing) build-docker-images
This focuses mainly on the job build-docker-image to ensure this actually works. Other jobs should mostly work. This is still a work in progress as we would need a way to declaratively deactivate some chronic jobs but baby steps.
This introduces a new variable node which allows to either run it on the built-in node (like actually with the production jenkins) or on the 'docker' agent node (which should be configured either prior to choose it).
This is actually useful for running in a local jenkins and hacking around those jobs. This will also allow further developement on similar jobs which requires to run docker. For example, the future build-docker-images.
This also drops the instruction updateGitlabCommitStatus which is not needed in that
job (since that won't be opened in a mr context).
