quote $ in Jenkins groovy (#168)

Author: adrpo

.CI/Jenkinsfile

@@ -584,12 +584,12 @@ SEPARATOR='/'
 HISTORY_FILE='00_history.html'
 
 for b in ${env.GITBRANCHES} ${env.GITBRANCHES_FMI} ${env.GITBRANCHES_NEWINST} ${env.GITBRANCHES_DAE} ${env.GITBRANCHES_CPP}; do
-  BRANCH=`echo ${b} | cut -d '/' -f2`
-  FILE="${HISTORY_DIRECTORY}${BRANCH}${SEPARATOR}${HISTORY_FILE}"
-  if [ ! -f ${FILE} ]; then
-    echo "Creating initial history: library.openmodelica.org:${FILE}"
-    ssh hudson@library.openmodelica.org mkdir -p ${HISTORY_DIRECTORY}${BRANCH}
-    ssh hudson@library.openmodelica.org touch ${FILE}
+  BRANCH=`echo \${b} | cut -d '/' -f2`
+  FILE="\${HISTORY_DIRECTORY}\${BRANCH}\${SEPARATOR}\${HISTORY_FILE}"
+  if [ ! -f \${FILE} ]; then
+    echo "Creating initial history: library.openmodelica.org: \${FILE}"
+    ssh hudson@library.openmodelica.org mkdir -p \${HISTORY_DIRECTORY}\${BRANCH}
+    ssh hudson@library.openmodelica.org touch \${FILE}
   fi
 done
 """