buiddebs: add an explicit "needs" on dotenv to tag_build

The dotenv job defines an artifacts: reports: dotenv that sets a number of required environment variables.

For some reason, moving this out into includes.yaml means it's not automatically passed onto the tag_build job, so we have to explicitly declare a needs: relationship to have the dotenv artifacts be available to the tag_build job.

Tested that this works via WIP.yml, which is now unnecessary again, so remove it.