fix calling the update target for host-only builds

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@14997 3c298f89-4303-0410-b956-a3cf2f4a3e73

include/host-build.mk

@@ -128,6 +128,7 @@ ifndef DUMP
     compile: host-compile
     install: host-install
     clean: host-clean
+    update: host-update
   else
     host-compile: $(HOST_STAMP_INSTALLED)
   endif