magento-test/dev/tools/grunt/configs/cssmin.json

{
  "options": {
    "report": "gzip",
    "keepSpecialComments": 0
  },
  "setup": {
    "files": {
      "<%= path.css.setup %>/setup.css": "<%= path.css.setup %>/setup.css"
    }
  },
  "updater": {
    "files": {
      "<%= path.css.updater %>/updater.css": "<%= path.css.updater %>/updater.css"
    }
  }
}