x86: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/config.mk b/arch/x86/config.mk
index b22959f..4a4ad80 100644
--- a/arch/x86/config.mk
+++ b/arch/x86/config.mk
@@ -31,7 +31,7 @@
 LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
 LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
 
-NORMAL_LIBGCC = $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+export NORMAL_LIBGCC = $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
 PREFIXED_LIBGCC = $(OBJTREE)/arch/$(ARCH)/lib/$(shell basename $(NORMAL_LIBGCC))
 
 export USE_PRIVATE_LIBGCC=$(shell dirname $(PREFIXED_LIBGCC))