Don't compile android.jar contents into smack-android jar
gradles compile command (which is deprecated and should be replaced with implementation) includes the arguments resources into the result jar.
That means that smack-android will contain resources found at the android boot classpath.
This results in a +~11mb increase in size of the resulting apk when including Smack as a composite build. The increase comes from 11mb of Android resources, mainly drawables.
compileOnly (formerly provided) on the other hand will assert that the android.jar classes are provided by the system, which is probably what we want in this case.