dump: add missing include

Change-Id: I617a9580216e4c579eebac702309b3610a8c6dcf

tools/dump/main.cpp

@@ -20,6 +20,8 @@
 #include "ndndump.hpp"
 #include "core/version.hpp"
 
+#include <ndn-cxx/util/ostream-joiner.hpp>
+
 #include <sstream>
 
 namespace ndn {