message: add -f to force cleanup of build images
diff: @@ -5,4 +5,4 @@ if ! docker -H ${DOCKER_HOST} info &> /dev/null; then
  fi
  # prune all images older than 7 days
  -docker image prune -a --filter "until=168h"
  +docker image prune -af --filter "until=168h"
  