title: maven-source-plugin not work for kotlin
body: <p>I am trying to use maven-source-plugin to create a source.jar for my kotlin project, but seems the maven-source-plugin not work well for kotlin project.</p>
  
  <p>when i run "mvn source:jar", the output message always says:</p>
  
  <pre><code>[INFO] No sources in project. Archive not created.
  </code></pre>
  
  <p>here is the maven-source-plugin configuration in my pom file of the project:</p>
  
  <pre><code>    &lt;build&gt;
      &lt;plugins&gt;
  
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-source-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.2.1&lt;/version&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;attach-sources&lt;/id&gt;
                      &lt;phase&gt;package&lt;/phase&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;jar&lt;/goal&gt;
                      &lt;/goals&gt;
                      &lt;configuration&gt;
                          &lt;attach&gt;true&lt;/attach&gt;
                          &lt;includes&gt;
           &lt;!-- i am trying to specify the include dir manually, but not work --&gt;                               
                           &lt;include&gt;${project.basedir}/src/main/kotlin/*&lt;/include&gt;
                          &lt;/includes&gt;
                          &lt;forceCreation&gt;true&lt;/forceCreation&gt;
                      &lt;/configuration&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
      &lt;/plugins&gt;
  &lt;/build&gt;
  </code></pre>
  
  <p>my question is: how to attach kotlin source files using maven-source-plugin?</p>
  
  <p>thanks ~~</p>