Summary:
Consolidate CocoaPods codegen scripts under a single `use_react_native_codegen!` method in `react_native_pods.rb`.
This is the first step towards making the codegen scripts library-agnostic. There are still a handful of hardcoded assumptions in place (e.g. the output directory structure, the use of a separate directory for components), but with some work one would be able to add codegen support to arbitrary CocoaPods podspecs.
The codegen script no longer takes a CODEGEN_PATH argument, and will instead attempt to use the local react-native-codegen package if available, and fallback to using the node_modules/react-native-codegen package if not.
## Usage
The `use_react_native_codegen!` method has two arguments:
- `spec`, a pod [Specification](https://www.rubydoc.info/github/CocoaPods/Core/Pod/Specification) object.
- `options`, an optional object. Supported keys:
- `:srcs_dir`, the path to your JavaScript sources. Your native module or component specs should be located somewhere in this directory.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D25728053
fbshipit-source-id: feec587b656d5b220598ce6196ea6bb34a9580a9