buildgcc: Deal with gmp on 32bit Cygwin on 64bit host

Similar to what the below change says,
(
 http://review.coreboot.org/10792
  commit ddb8f80894
  Author: Patrick Georgi <patrick@georgi-clan.de>
  Date:   Sat Jul 4 17:45:54 2015 +0200

    buildgcc: Deal with gmp on 32bit Linux on 64bit CPUs

    GMP is overeager to detect 64bit ABIs even if the entire running codebase is
    32bit (but on a 64bit CPU). Enforce a 32bit build in that situation.
)
building GMP can not detect Cygwin is 32bit either if the
host which Cygwin is running is 64bit. We set ABI=32
in that case.

Change-Id: Ic53d75defebbe902325eb07f3d8631b2a53245ef
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/11123
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/crossgcc/buildgcc

@@ -622,7 +622,7 @@ if [ $UNAME = "Darwin" ]; then
 	if $CC -v 2>&1 | grep -q LLVM; then
 		CC=llvm-gcc
 	fi
-elif [ $UNAME = "Linux" ]; then
+elif [ $UNAME = "Linux" -o $UNAME = "Cygwin" ]; then
 	# gmp is overeager with detecting 64bit CPUs even if they run
 	# a 32bit kernel and userland.
 	if [ "$(uname -m 2>/dev/null)" = "i686" ]; then