Adds ability to save config into a file

Author: lukaszlenart

src/main/java/com/akathist/maven/plugins/launch4j/Launch4jMojo.java

@@ -286,6 +286,18 @@ public class Launch4jMojo extends AbstractMojo {
     @Parameter
     private File manifest;
 
+    /**
+     * If set to true it will save final config into a XML file
+     */
+    @Parameter(defaultValue = "false")
+    private boolean saveConfig = false;
+
+    /**
+     * If {@link #saveConfig} is set to true, config will be written to this file
+     */
+    @Parameter(defaultValue = "${project.build.directory}/launch4j-config.xml")
+    private File configOutfile;
+
     private File getJar() {
         return new File(jar);
     }
@@ -404,6 +416,14 @@ public void execute() throws MojoExecutionException {
             getLog().error(e);
             throw new MojoExecutionException("Failed to build the executable; please verify your configuration.", e);
         }
+
+        if (saveConfig) {
+            try {
+                ConfigPersister.getInstance().save(configOutfile);
+            } catch (ConfigPersisterException e) {
+                throw new MojoExecutionException("Cannot save config into a XML file", e);
+            }
+        }
     }
 
     /**