[autodevops] use GITLAB_ENVIRONMENT_URL as CW_BASE_URL
When deploying a cube using the AutoDevops pipeline the base environment contains $GITLAB_ENVIRONMENT_URL which gives the URL being served by the review app.
Maybe this environment variable can be "translated" into CW_BASE_URL in the entrypoint ?
Not sure if this should be done here or in cubicweb, here is the cubicweb related issue : cubicweb#386 (closed)