When migrating to expo cli instead of react-native cli I noticed one build feature that is missing which is pretty nice to reduce build times.

reactNativeArchitectures allows gradle to build c++ only for these architectures instead of all of them. If you have a single emulator running this basically reduces native build times by 75%.

It works by getting the cpu architecture of all running emulators and passing that to gradle.

Implementation in rn-cli: https://github.com/react-native-community/cli/blob/main/packages/cli-platform-android/src/commands/buildAndroid/index.ts#L58-L77.