[modelcars] add role to build image

[drewrip]

I've got this working locally but need to make sure it works in the CI

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[kpouget]

from the github action:

23:48:40 ERROR [validate_role_files.py:101] pvc_template: templates/pvc.yml.j2 --> not found

I think you don't want this line

[kpouget]

thanks Drew, looks good :)
minor comments, you need to regenerate the auto-generate files (I need to update the doc ...)

./run_toolbox.py repo generate_toolbox_related_files

and remove the PVC variable

with that fixed, good to merge from my POV