[PATCH v2] kbuild: add KBUILD_DEFCONFIG

[Masahiro Yamada]

This allows "make ARCH=... defconfig".

Fox example, you can type "make defconfig" instead of
"make sandbox_defconfig".

Signed-off-by: Masahiro Yamada <yamada.m at jp.panasonic.com>
---

Changes in v2:
  - Add it only to sandbox, x86, efi.

 arch/efi/Makefile     | 2 ++
 arch/sandbox/Makefile | 1 +
 arch/x86/Makefile     | 2 ++
 3 files changed, 5 insertions(+)

diff --git a/arch/efi/Makefile b/arch/efi/Makefile
index 85cb655..b078bd0 100644
--- a/arch/efi/Makefile
+++ b/arch/efi/Makefile
@@ -1,3 +1,5 @@
+KBUILD_DEFCONFIG := efi_defconfig
+
 CFLAGS += -fpic -fshort-wchar -mno-sse -mno-mmx
 
 ifeq ($(CONFIG_X86_32),y)
diff --git a/arch/sandbox/Makefile b/arch/sandbox/Makefile
index ed5d3a3..e3fb039 100644
--- a/arch/sandbox/Makefile
+++ b/arch/sandbox/Makefile
@@ -1,3 +1,4 @@
+KBUILD_DEFCONFIG := sandbox_defconfig
 
 CPPFLAGS += -D__SANDBOX__ -fno-strict-aliasing
 
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index a78fa22..da17d70 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -1,3 +1,5 @@
+KBUILD_DEFCONFIG := generic_defconfig
+
 CPPFLAGS += -D__X86__ -fno-strict-aliasing
 
 board-y := x86_generic
-- 
1.9.1