Isolate Kconfig host compiler options

This reverts commit 645f2dd5d97ffbaa80da7fbd776a08a76eb758e3.

Instead of adding a special case to nvramtool to avoid it
picking up Kconfig's regex.h, have the host compiler only
consider util/kconfig for includes (ie. -Iutil/kconfig)
for kconfig related object files.

Change-Id: Ie4f97ce38cb3e911f6e6c1e5b6f86f6998d93f69
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/1509
Tested-by: build bot (Jenkins)
Reviewed-by: Zheng Bao <zheng.bao@amd.com>
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>
diff --git a/Makefile b/Makefile
index 2723efb..44fd62f 100644
--- a/Makefile
+++ b/Makefile
@@ -76,8 +76,8 @@
 
 HOSTCC = gcc
 HOSTCXX = g++
-HOSTCFLAGS := -I$(srck) -I$(objk) -g
-HOSTCXXFLAGS := -I$(srck) -I$(objk)
+HOSTCFLAGS := -g
+HOSTCXXFLAGS := -g
 LIBGCC_FILE_NAME := $(shell test -r `$(CC) -print-libgcc-file-name` && $(CC) -print-libgcc-file-name)
 
 DOXYGEN := doxygen