configure: add missing INCLUDE to netnsid detection

Fixes: d116ff34 ("ip netns: Fix rtnl error while print netns list")
Signed-off-by: Jiri Benc <jbenc@redhat.com>

configure

@@ -224,7 +224,7 @@ check_netnsid()
 #include <linux/rtnetlink.h>
 int test_def = RTM_GETNSID;
 EOF
-    $CC -c $TMPDIR/netnsid.c >/dev/null 2>&1
+    $CC -I$INCLUDE -c $TMPDIR/netnsid.c >/dev/null 2>&1
     if [ $? -eq 0 ]
     then
 	echo "IP_CONFIG_NETNSID:=y" >> Config