Add maven.changelog.basedir property for users that don't use basedir directory for checkout.

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-1/plugins/trunk@114669 13f79535-47bb-0310-9956-ffa450edef68

developer-activity/plugin.jelly

@@ -60,7 +60,7 @@
           
           <j:if test="${changelogPresent != 'true'}">
             <changelog:changelog
-              basedir="${basedir}"
+              basedir="${maven.changelog.basedir}"
               developers="${pom.developers}"
               factory="${factory}"
               output="${maven.build.dir}/changelog.xml"