Don't check DAGSTER_REPO environment variable when building docker images
This default causes releases happening in a fresh git checkout to still use your standard git checkout - last week this caused the docker builds to accidentally update the previous release instead of creating a new one. Instead, require the docker image build command to be run inside the dagster repo you want to ue
Let me know if there are any other workflows that will not work as expected if we make this change - for example, something in the internal repo perhaps??
Test Plan: So far: dagster-image build-all --name k8s-dagit --dagster-version 0.9.12 inside and outside of a git repo
Reviewers: johann, nate
Reviewed By: nate
Differential Revision: https://dagster.phacility.com/D4666