Function enable_pipe_nonblock

compat/nonblock.c:6–13

#ifdef O_NONBLOCK

int enable_pipe_nonblock(int fd)
{
	int flags = fcntl(fd, F_GETFL);
	if (flags < 0)
		return -1;
	flags |= O_NONBLOCK;
	return fcntl(fd, F_SETFL, flags);
}

#elif defined(GIT_WINDOWS_NATIVE)