Add email challenge module

Refs: #4053

Change-Id: Ic5093fa484df967a760d7503eab2436f5794a385
diff --git a/.jenkins.d/01-ndn-cxx.sh b/.jenkins.d/01-ndn-cxx.sh
index 482c155..31bb9e4 100755
--- a/.jenkins.d/01-ndn-cxx.sh
+++ b/.jenkins.d/01-ndn-cxx.sh
@@ -16,6 +16,10 @@
 
 LATEST_VERSION=$((cd ndn-cxx-latest && git rev-parse HEAD) 2>/dev/null || echo UNKNOWN)
 
+if has OSX $NODE_LABELS; then
+    LATEST_VERSION=""
+fi
+
 if [[ $INSTALLED_VERSION != $LATEST_VERSION ]]; then
     sudo rm -Rf ndn-cxx
     mv ndn-cxx-latest ndn-cxx