buildgcc: Help GMP build with 32-bit NetBSD

GMP's configure tries to build for 64-bit with a 32-bit userspace on
NetBSD too. Help it by forcing ABI=32.

Change-Id: I290ea0ef1626fdd88dc3ff74fadb9578ef6a1c9c
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/13067
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

util/crossgcc/buildgcc

@@ -688,6 +688,11 @@ elif [ $UNAME = "Linux" -o $UNAME = "Cygwin" ]; then
 	if [ "$(uname -m 2>/dev/null)" = "i686" ]; then
 		OPTIONS="ABI=32"
 	fi
+elif [ $UNAME = "NetBSD" ]; then
+	# same for NetBSD but this one reports an i386
+	if [ "$(uname -m 2>/dev/null)" = "i386" ]; then
+		OPTIONS="ABI=32"
+	fi
 fi
 fi # GCC