.babelrc hack needs content for the tests only

package.json

@@ -37,14 +37,16 @@
   },
   "scripts": {
     "check-gb-unused-babelrc": "cd gutenberg/; git ls-files --error-unmatch .babelrc 2>/dev/null; tracked=$?; cd ..; (if [ \"$tracked\" -gt 0 ]; then (exit 0); else (echo \"'.babelrc' is tracked in Gutenberg, cannot overwrite!\"; exit 1); fi)",
-    "bypass-gb-babel": "echo '{\"presets\": [\"@wordpress/default\"]}' > gutenberg/.babelrc",
+    "bypass-gb-babel": "echo '{}' > gutenberg/.babelrc",
+    "test:bypass-gb-babel": "echo '{\"presets\": [\"@wordpress/default\"]}' > gutenberg/.babelrc",
     "pre-build": "yarn check-gb-unused-babelrc && yarn bypass-gb-babel",
+    "test:pre-build": "yarn check-gb-unused-babelrc && yarn test:bypass-gb-babel",
     "start": "yarn pre-build && yarn react-native start",
     "start:reset": "yarn clean:runtime && yarn start --reset-cache",
     "start:debug": "yarn pre-build && node --inspect-brk node_modules/.bin/react-native start",
     "android": "react-native run-android",
     "ios": "react-native run-ios",
-    "test": "yarn pre-build && cross-env NODE_ENV=test node node_modules/jest/bin/jest.js --verbose --config jest.config.js",
+    "test": "yarn test:pre-build && cross-env NODE_ENV=test node node_modules/jest/bin/jest.js --verbose --config jest.config.js",
     "test:debug": "yarn pre-build && cross-env NODE_ENV=test node --inspect-brk node_modules/jest/bin/jest.js --runInBand --verbose --config jest.config.js",
     "flow": "flow",
     "prettier": "prettier-eslint --write $npm_package_config_jsfiles $npm_package_config_scssfiles",