gnutls: Avoid building unused gnutls dependency

Avoid building unused gnutls dependency

Signed-off-by: Boris Krasnovskiy <borkra@gmail.com>
(cherry picked from commit 32f4d46f51)

libs/gnutls/Makefile

@@ -103,7 +103,7 @@ endef
 define Package/libgnutls-dane
 $(call Package/gnutls/Default)
   TITLE+= (libgnutls-dane library)
-  DEPENDS:= +libgnutls +libunbound
+  DEPENDS:= +libgnutls +PACKAGE_libgnutls-dane:libunbound
 endef
 
 define Package/libgnutls/description