Clear out .cxx dir during gradle clean task. Directory is DOTcxx, not just cxx

It's an additional build dir

Author: ViliusSutkus89

app/build.gradle

@@ -170,3 +170,9 @@ dependencies {
     implementation 'androidx.test.espresso:espresso-idling-resource:3.5.1'
     implementation 'androidx.annotation:annotation:1.8.0'
 }
+
+tasks.named("clean") {
+    doLast {
+        delete(new File(projectDir, ".cxx"))
+    }
+}