Drop timestamps from docker build for reproducible image hashes

.gitlab-ci.yml

@@ -10,6 +10,7 @@ docker-build:
       --context "${CI_PROJECT_DIR}"
       --dockerfile "${CI_PROJECT_DIR}/Dockerfile"
       --destination "${DOCKER_IMAGE_NAME}"
+      --reproducible
   rules:
     - if: $CI_COMMIT_BRANCH
       exists: