Fix build problems under Cygwin

This patch allows u-boot to build without error in a cygwin
environment.  Cygwin does not define __u64 in it's
include/asm/types.h file.  The -idirafter flag in the u-boot
build causes the inclusion of the cygwin types.h file as opposed
to u-bot/include/asm/types.h file which does define __u64.
Subsequently, sha1.c compile fails due to unknown symbol.

Signed-off-by: Brian Miller <raptorbrino@netscape.net>

tools/Makefile

@@ -97,6 +97,7 @@ endif
 #
 ifeq ($(HOSTOS),cygwin)
 SFX = .exe
+HOST_CFLAGS += -ansi
 else
 SFX =
 endif