fix missing the FILE field..

fix  Download/default is missing the FILE field..  Stop. error on openwrt

package/openwrt/Makefile

@@ -9,6 +9,9 @@ PKG_NAME:=smartdns
 PKG_VERSION:=1.2019.28
 PKG_RELEASE:=1
 
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
+PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
+
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://www.github.com/pymumu/smartdns.git
 PKG_SOURCE_VERSION:=982002e836e486fb4e360bc10e84e7e7197caf46