Define root element as var.

Jenkinsfile

@@ -66,13 +66,14 @@ pipeline {
                    echo "#Build ${PIPELINE_BUILD_NUMBER},," > $ACTION_REPORT
                    echo "#StartTime ${date},," >> $ACTION_REPORT
                    echo "Project,Repo,Result" >> $ACTION_REPORT
-                   echo -e "<actions from=\"${ACTION_URL}\">" > $ACTION_OUTPUT
                    '''
             }
         }
         stage('clone and exec') {
             steps {
                 script {
+                    def start_el = "<actions from=\"${actionURL}\">"
+                    sh "echo -e '${start_el}' >> $ACTION_OUTPUT"
                     for (int i = 0; i < projects.size(); i++) {
                         stage(projects[i]) {
                             echo "About to execute over ${projects[i]}"