include: r39979 broke kernel unpacking

Signed-off-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 40002

include/kernel-defaults.mk

@@ -31,7 +31,7 @@ Kernel/Patch:=$(Kernel/Patch/Default)
 ifeq ($(strip $(CONFIG_EXTERNAL_KERNEL_TREE)),"")
   ifeq ($(strip $(CONFIG_KERNEL_GIT_CLONE_URI)),"")
     define Kernel/Prepare/Default
-	xzcat $(DL_DIR)/$(LINUX_SOURCE) | $(TAR) -C $(KERNEL_BUILD_DIR) $(TAR_OPTIONS)
+	xzcat $(DL_DIR)/$(LINUX_SOURCE) | $(TAR) -C $(KERNEL_BUILD_DIR) -xf -
 	$(Kernel/Patch)
 	touch $(LINUX_DIR)/.quilt_used
     endef