bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 36405@debbugs.gnu.org, kbrown@cornell.edu
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Fri, 28 Jun 2019 23:26:09 -0700
> 
> Eli Zaretskii wrote:
> > What problems did you see/envision on other platforms with the
> > original patch?
> 
> Mainly the hassle of maintaining code with a lot of hard-to-read ifdefs in it. 
> It's better if system-specific stuff is kept to a minimum in mainline code. 

I agree, of course.  But in this case we are talking about adding 2
#ifdef's, so the situation is not much worse than it was before.

> Also, this O_PATH stuff is not that high of a priority, as the code works quite 
> well in practice without O_PATH.

It was evidently important enough for us to use it on platforms that
support it.

> How about something like the attached patch instead? It's simpler and should be 
> a bit faster on Cygwin than the original patch. I haven't tested it.

Thanks, this is fine with me if it does the job.  Ken?