iproute2: add libutil to InstallDev section

In iproute2 v4.17 ll_map has been moved from the libnetlink to the libutil
library; add libutil as well to the staging dir in order to keep support
for ll_map

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

package/network/utils/iproute2/Makefile

@@ -135,6 +135,7 @@ define Build/InstallDev
 	$(CP) $(PKG_BUILD_DIR)/include/{libgenl,libnetlink,ll_map}.h $(1)/usr/include/
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(CP) $(PKG_BUILD_DIR)/lib/libnetlink.a $(1)/usr/lib/
+	$(CP) $(PKG_BUILD_DIR)/lib/libutil.a $(1)/usr/lib/
 endef
 
 define Package/ip-tiny/install