message: build only one layer for the base image
  => improves the performance
diff: @@ -9,6 +9,8 @@ variables:
  GIT_SUBMODULE_STRATEGY: normal
  FF_GITLAB_REGISTRY_HELPER_IMAGE: 1
  +# Build docker image with kaniko
  +# kaniko does not require DinD or a shell runner.
  .prepare:docker: &prepare_docker
  stage: prepare
  image:
  @@ -21,7 +23,7 @@ variables:
  --context ${CI_PROJECT_DIR}
  --dockerfile ${CI_PROJECT_DIR}/Dockerfile
  --destination ${DOCKER_IMAGE}:${DOCKER_TAG}
  - --snapshotMode=redo
  + --single-snapshot
  prepare:docker:
  <<: *prepare_docker
  