feat: Add comment to describe var exports

.gitlab-ci.yml

@@ -62,6 +62,7 @@ workflow:
   - export CRI_XCBC_prod=$(git rev-parse --short origin/uab-prod)
   - git fetch upstream ${EXT_PR_SRC_BRANCH}
   - git merge upstream/${EXT_PR_SRC_BRANCH}
+  # export vars into job artifacts
   - cd ..
   - export PACKER_IMAGE_HEAD=$(git rev-parse --short HEAD)
   - echo CRI_XCBC_HEAD=${CRI_XCBC_HEAD} | tee -a $CI_PROJECT_DIR/image.env