.circlerc, $BASH_ENV, $ENV

Build Environment
4

If you can use the multi-line format of the run step, adding in another line doesn’t seem too onerous. You could even have a quick linter to ensure it is present in every step:

  - run:
      name: Save Docker image layer cache
      command: |
        sh /tmp/run-me.sh
        mkdir -p /caches
        docker save -o /caches/${CIRCLE_PROJECT_REPONAME}.tar ${CIRCLE_PROJECT_REPONAME}

Adding that run-me.sh manually doesn’t seem to harm readability too much?