Makefile: fix i18n build with ubus

Commit caf4d571e6d86285a3690cfcc8de9c5f394320a8 forgot adding
ubus_libs to build_libs for all-i18n target

Fixes:
 - http://autobuild.buildroot.org/results/c0b27754b7ede024c095bdf0b3616e6f6be48c6d

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
diff --git a/Makefile b/Makefile
index 3fb7cbe..78e25f0 100644
--- a/Makefile
+++ b/Makefile
@@ -111,7 +111,7 @@
  top="$(top)" \
  i18n=-DLOCALEDIR=\'\"$(LOCALEDIR)\"\' \
  build_cflags="$(version) $(dbus_cflags) $(idn2_cflags) $(idn_cflags) $(ct_cflags) $(lua_cflags) $(nettle_cflags)" \
- build_libs="$(dbus_libs) $(idn2_libs) $(idn_libs) $(ct_libs) $(lua_libs) $(sunos_libs) $(nettle_libs) $(gmp_libs)"  \
+ build_libs="$(dbus_libs) $(idn2_libs) $(idn_libs) $(ct_libs) $(lua_libs) $(sunos_libs) $(nettle_libs) $(gmp_libs) $(ubus_libs)"  \
  -f $(top)/Makefile dnsmasq
 	for f in `cd $(PO); echo *.po`; do \
 		cd $(top) && cd $(BUILDDIR) && $(MAKE) top="$(top)" -f $(top)/Makefile $${f%.po}.mo; \