Summary:
The ART library backend did not get build support for tvOS when other libraries did. We are writing an application that will run on tvOS, and wanted to use ART, so it was important to have this. This PR adds that build support.
Verified that this builds and works on tvOS simulator for development of this project.
Closes https://github.com/facebook/react-native/pull/12547
Differential Revision: D4925864
Pulled By: lacker
fbshipit-source-id: f72c650d7620e9c7f59d9ae68cfc39f0e7bab12b
32eab54781