kconfig: allow specifying the target for savedefconfig

Change-Id: Iee5ab0d3bdc8b754669356f2046d290d9ca555c2
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10511
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/util/kconfig/Makefile b/util/kconfig/Makefile
index f80d531..6c301a9 100644
--- a/util/kconfig/Makefile
+++ b/util/kconfig/Makefile
@@ -5,6 +5,8 @@
 export LC_ALL=C
 export LANG=C
 
+DEFCONFIG?=defconfig
+
 PHONY += oldconfig xconfig gconfig menuconfig config silentoldconfig update-po-config \
 	localmodconfig localyesconfig
 
@@ -85,7 +87,7 @@
 	$< --$@ $(Kconfig)
 
 savedefconfig: $(objk)/conf
-	$< --$@=defconfig $(Kconfig)
+	$< --$@=$(DEFCONFIG) $(Kconfig)
 
 defconfig: $(objk)/conf
 ifeq ($(KBUILD_DEFCONFIG),)