android: Print deprecated warnings

android/build.gradle

@@ -38,3 +38,9 @@ subprojects {
 task clean(type: Delete) {
     delete rootProject.buildDir
 }
+
+gradle.projectsEvaluated {
+    tasks.withType(JavaCompile) {
+        options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
+    }
+}