Change CI config so that it finds more breakages

Previously we did not run lint and did not try to compile the
AndroidTest instrumentation tests.

briar-android/build.gradle

@@ -82,6 +82,8 @@ android {
 		warning 'MissingTranslation'
 		warning 'ImpliedQuantity'
 		warning 'ExtraTranslation'
+		// FIXME
+		warning 'InvalidPackage'
 	}
 }