Add a dummy test for 'buildPlugin' support (#7)

pom.xml

@@ -22,6 +22,11 @@
       <artifactId>metainf-services</artifactId>
       <version>1.9</version>
     </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <scm>

src/test/java/jenkins/Junit4DummyTest.java

@@ -0,0 +1,14 @@
+package jenkins;
+
+import org.junit.Test;
+
+public class Junit4DummyTest {
+
+    @Test
+    public void anything() {
+        /*
+         * Intentionally blank. We just want a test that runs with JUnit so that buildPlugin() works
+         * in the Jenkinsfile.
+         */
+    }
+}