Remove android/build_android.sh.

build_android.sh is broken and fixing it seems not be worth it.
Especially since building on android is already well supported
using ndk-build.

build_android.sh is also dependent on android-cmake, which is
recently has been a flakey dependency.

Change-Id: I8a22e6e2ef7f1708cd23bd38e33eb17189666509