add diagnostics output plugin

Signed-off-by: Raymond Auge <rotty3000@apache.org>
diff --git a/pom.xml b/pom.xml
index 901bbae..df2c101 100644
--- a/pom.xml
+++ b/pom.xml
@@ -688,6 +688,29 @@
         </pluginManagement>
         <plugins>
             <plugin>
+                <!--
+                    This is used for diagnostics by invoking it like:
+
+                    mvn antrun:run@props [-N]
+                -->
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-antrun-plugin</artifactId>
+                <version>3.0.0</version>
+                <executions>
+                    <execution>
+                        <id>props</id>
+                        <goals>
+                            <goal>run</goal>
+                        </goals>
+                        <configuration>
+                            <target>
+                                <echoproperties />
+                            </target>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
                 <groupId>org.codehaus.mojo</groupId>
                 <artifactId>flatten-maven-plugin</artifactId>
                 <version>1.2.7</version>