nvramtool: Set build flags for FreeBSD

Set HOSTCFLAGS as nil to make the nvramtool include the regex.h
in system. Otherwise it will include the regex.h in kconfig, which
will cause building error in FreeBSD.

Change-Id: I95292e23e1716da1260842be9597119a4e26c8ed
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/1500
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>
Tested-by: build bot (Jenkins)

util/nvramtool/Makefile.inc

@@ -27,6 +27,10 @@ endif
 ifeq ($(OS_ARCH), NetBSD)
 NVRAMTOOLLDLFLAGS = -l$(shell uname -p)
 endif
+ifeq ($(OS_ARCH), FreeBSD)
+NVRAMTOOLFLAGS += -O2 -g -Wall -W
+HOSTCFLAGS =
+endif
 ifeq ($(shell uname -o), Cygwin)
 NVRAMTOOLFLAGS += -O2 -g -Wall -W -D__GLIBC__
 NVRAMTOOLLDFLAGS = -lioperm