Update build instructions
Update build instructions

syncthing/syncthing-android,syncthing/syncthing-android,Nutomic/syncthing-android,syncthing/syncthing-android,Nutomic/syncthing-android,flipreverse/syncthing-android,jmintb/syncthing-android,flipreverse/syncthing-android,jmintb/syncthing-android