Summary:This adds a BUCK file to UIExplorer to allow building it with buck. It is based on the one in the movies app but I removed the extra deps that were not needed in both files.
Also add build version number and target sdk version in the Android manifest so Buck can use it since it was only specified in the gradle build and caused the app to run on a super old target sdk.
bestander mkonicek Would it be simple to also build the ndk part with Buck? Right now it is built with gradle and packaged after. I suppose it is already being done internally at facebook. The BUCK files for building the cpp code are already there but I couldn't figure out what was missing to make it work :(
That is pretty much the only missing part to have first class support for building RN apps with Buck in OSS. We could eventually include BUCK files with the generated project.
**Test plan (required)**
Build and run UIExplorer and Movies examples using Buck.
Edited:
```
./gradlew ReactAndroid:packageReactNdkLibsForBuck
Closes https://github.com/facebook/react-native/pull/6399
Reviewed By: mkonicek
Differential Revision: D3042355
Pulled By: bestander
fb-gh-sync-id: 74760c7ba12d35b1853d2e3706c2ba130f9eef1c
fbshipit-source-id: 74760c7ba12d35b1853d2e3706c2ba130f9eef1c
Janic Duplessis
Konstantin Raev
Martin Konicek