Summary:
Use generate-artifacts.js script when USE_CODEGEN_DISCOVERY envvar is set to 1 at `pod install` time. Setting this envvar will disable the old codegen script.
Added `[Codegen]` prefix to all codegen log output.
Note: This script is not ready for production use at the moment.
Changelog: [Internal]
Reviewed By: sota000
Differential Revision: D31693778
fbshipit-source-id: 25da95bdb33315ac42c6dfb40334e22ec9823cb1