build: check for linux/genetlink.h

Change-Id: Id18fcc81a49e769a05c4416cdce03022a2179051
Refs: #4020
diff --git a/src/net/network-monitor.cpp b/src/net/network-monitor.cpp
index 89af14a..57ef7f1 100644
--- a/src/net/network-monitor.cpp
+++ b/src/net/network-monitor.cpp
@@ -31,7 +31,7 @@
 #if defined(NDN_CXX_HAVE_OSX_FRAMEWORKS)
 #include "detail/network-monitor-impl-osx.hpp"
 #define NETWORK_MONITOR_IMPL_TYPE NetworkMonitorImplOsx
-#elif defined(NDN_CXX_HAVE_RTNETLINK)
+#elif defined(NDN_CXX_HAVE_NETLINK)
 #include "detail/network-monitor-impl-netlink.hpp"
 #define NETWORK_MONITOR_IMPL_TYPE NetworkMonitorImplNetlink
 #else