update unit test support in build files

OpenKeychain/src/androidTest/java/tests/SomeTest.java

@@ -0,0 +1,12 @@
+package tests;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SomeTest {
+    @Test
+    public void willFail() {
+        // stub
+        // Assert.assertThat();
+    }
+}