Only specify the Android ABI to CMake that Gradle is already building

Currently, when you build a specific ABI for Android, we still tell CMake to build all the ABIs we support. This makes the build three times slower than it needs to be when you first build for a specific target ABI. This should be configured in Apps/Playground/node_modules/@babylonjs/react-native/android/build.gradle. An example of what I believe to be the correct way to configure this can be found here: https://stackoverflow.com/questions/55479984/pass-architecture-information-from-gradlew-command-to-cmake/55486008#55486008