busybox: busybox-update-config should depend on busybox-configure

Before the config file can be copied, it has to exist.  The
other xxx-update-config targets do this as well.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/busybox/busybox.mk

@@ -223,5 +223,5 @@ busybox-menuconfig busybox-xconfig busybox-gconfig: busybox-patch
 	rm -f $(BUSYBOX_DIR)/.stamp_built
 	rm -f $(BUSYBOX_DIR)/.stamp_target_installed
 
-busybox-update-config:
+busybox-update-config: busybox-configure
 	cp -f $(BUSYBOX_BUILD_CONFIG) $(BUSYBOX_CONFIG_FILE)