[coreboot] [help]build cbfstool fail with cygwin64

[kurt qiao]

don't know why my email didn't receive in the list, so i reply again:
i finally built pass with define:

CFLAGS += -std=gnu99  in cbfstool/Makefile
TOOLCFLAGS ?= -std=gnu99  in cbfstool/Makefile.inc

and change cbfstool.c code to :
--  if (tolower(suffix[0])=='k') {
++ if (tolower((int)suffix[0])=='k') {

--  if (tolower(suffix[0])=='m') {
++ if (tolower((int)suffix[0])=='m') {