build: check for linux/genetlink.h

Change-Id: Id18fcc81a49e769a05c4416cdce03022a2179051
Refs: #4020
diff --git a/src/net/detail/network-monitor-impl-netlink.hpp b/src/net/detail/network-monitor-impl-netlink.hpp
index cbb0166..7870236 100644
--- a/src/net/detail/network-monitor-impl-netlink.hpp
+++ b/src/net/detail/network-monitor-impl-netlink.hpp
@@ -27,7 +27,7 @@
 #include "ndn-cxx-config.hpp"
 #include "../network-monitor.hpp"
 
-#ifndef NDN_CXX_HAVE_RTNETLINK
+#ifndef NDN_CXX_HAVE_NETLINK
 #error "This file should not be included ..."
 #endif