busybox: fix build issues

Fixes: f704f97e4c ("busybox: Include hdparm by default on nas type device")
Signed-off-by: John Crispin <john@phrozen.org>

package/utils/busybox/Makefile

@@ -92,10 +92,12 @@ ifneq ($(findstring c,$(OPENWRT_VERBOSE)),)
 endif
 
 define Build/Configure
+	rm -f $(PKG_BUILD_DIR)/.config
+	touch $(PKG_BUILD_DIR)/.config
 ifeq ($(DEVICE_TYPE),nas)
 	echo "CONFIG_HDPARM=y" >> $(PKG_BUILD_DIR)/.config
 endif
-	grep 'CONFIG_BUSYBOX_$(BUSYBOX_SYM)' $(TOPDIR)/.config | sed -e "s,\\(# \)\\?CONFIG_BUSYBOX_$(BUSYBOX_SYM)_\\(.*\\),\\1CONFIG_\\2,g" > $(PKG_BUILD_DIR)/.config
+	grep 'CONFIG_BUSYBOX_$(BUSYBOX_SYM)' $(TOPDIR)/.config | sed -e "s,\\(# \)\\?CONFIG_BUSYBOX_$(BUSYBOX_SYM)_\\(.*\\),\\1CONFIG_\\2,g" >> $(PKG_BUILD_DIR)/.config
 	yes 'n' | $(MAKE) -C $(PKG_BUILD_DIR) $(MAKE_FLAGS) oldconfig
 endef