improve java 9 build

git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia-tools/trunk@1807928 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 48aa877..470c5d6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -93,6 +93,15 @@
   </dependencies>
 
   <build>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>org.codehaus.plexus</groupId>
+          <artifactId>plexus-component-metadata</artifactId>
+          <version>1.7.1</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
     <plugins>
       <plugin>
         <groupId>org.codehaus.modello</groupId>