cbfstool: Allow anonymous structs/unions for older gcc versions

Older gcc versions throws a warning when a struct or union is
declared without a valid name (anonymous). This patch enables the
feature for older gcc versions so that no warning will be issued.

Change-Id: Idc5481f4d5723c5090a6f7d7dbb0686a737e11fc
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: http://review.coreboot.org/11779
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/util/cbfstool/Makefile.inc b/util/cbfstool/Makefile.inc
index 4994757..32c9282 100644
--- a/util/cbfstool/Makefile.inc
+++ b/util/cbfstool/Makefile.inc
@@ -60,6 +60,7 @@
 TOOLCPPFLAGS += -I$(top)/3rdparty/vboot/firmware/include
 TOOLCPPFLAGS += -I$(top)/3rdparty/vboot/firmware/2lib/include
 TOOLLDFLAGS ?=
+HOSTCFLAGS += -fms-extensions
 
 ifeq ($(shell uname -s | cut -c-7 2>/dev/null), MINGW32)
 TOOLCFLAGS += -mno-ms-bitfields