Summary:
This allows folks with a monorepo setup for React Native to set a simple configuration on the "Bundle React Native code and images" phase. This is because the bundler was configured to look for node_modules in a specific place, but in a monorepo your node_modules may be at the root one layer lower than a default configuration.
This same pattern of overriding this variable exists in the [react-native-xcode](https://github.com/facebook/react-native/blob/main/scripts/react-native-xcode.sh#L63) file.
Fixes: https://github.com/facebook/react-native/issues/33636 - "Unable to resolve module index"
```
Error: Unable to resolve module ./index from /Volumes/Nexus/Projects/xxx/.:
None of these files exist:
* index(.native|.android.js|.native.js|.js|.android.jsx|.native.jsx|.jsx|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)
* index/index(.native|.android.js|.native.js|.js|.android.jsx|.native.jsx|.jsx|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)
```
## Changelog
[General] [Added] - Add support for overriding `PROJECT_ROOT` during bundle steps for monorepos.
Pull Request resolved: https://github.com/facebook/react-native/pull/35354
Test Plan: Working CI build via CircleCI.
Reviewed By: cipolleschi
Differential Revision: D41319439
Pulled By: ryancat
fbshipit-source-id: 8516e54436b0a9d4b9df1efeee8e62c95d4d35b2
Connor Tumbleson
4d7ddd445c