Summary:
To make React Native play nicely with our internal build infrastructure we need to properly namespace all of our header includes.
Where previously you could do `#import "RCTBridge.h"`, you must now write this as `#import <React/RCTBridge.h>`. If your xcode project still has a custom header include path, both variants will likely continue to work, but for new projects, we're defaulting the header include path to `$(BUILT_PRODUCTS_DIR)/usr/local/include`, where the React and CSSLayout targets will copy a subset of headers too. To make Xcode copy headers phase work properly, you may need to add React as an explicit dependency to your app's scheme and disable "parallelize build".
Reviewed By: mmmulani
Differential Revision: D4213120
fbshipit-source-id: 84a32a4b250c27699e6795f43584f13d594a9a82
