Add `build` function to the prepare-ios-script (#49363)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49363

This change adds the `build()` function that calls xcodebuild to prepare the ReactNativeDependencies.framework

This functio creates the frameworks in the /react-native/third-party/.build folder

## Changelog:
[Internal] - Add build folder to the `prepare-ios-script`

Reviewed By: cortinico

Differential Revision: D69533218

fbshipit-source-id: edc9281e9270970084aa0f56b52ced4579df3473