Update build-for-devtools script to prepare unit tests too (facebook#21182)

Author: Brian Vaughn

package.json

@@ -108,7 +108,7 @@
   "scripts": {
     "build": "node ./scripts/rollup/build.js",
     "build-combined": "node ./scripts/rollup/build-all-release-channels.js",
-    "build-for-devtools": "cross-env RELEASE_CHANNEL=experimental yarn build react/index,react-dom,react-is,react-debug-tools,scheduler,react-test-renderer,react-refresh --type=NODE",
+    "build-for-devtools": "cross-env RELEASE_CHANNEL=experimental yarn build react/index,react-dom,react-is,react-debug-tools,scheduler,react-test-renderer,react-refresh --type=NODE && rm -rf build2 && mkdir build2 && cp -r ./build/node_modules build2/oss-experimental/",
     "build-for-devtools-dev": "yarn build-for-devtools --type=NODE_DEV",
     "build-for-devtools-prod": "yarn build-for-devtools --type=NODE_PROD",
     "linc": "node ./scripts/tasks/linc.js",