bug#50818: 28.0.50; .eln files need to be executable on Cygwin

[Eli Zaretskii]

> From: Ken Brown <kbrown@cornell.edu>
> Cc: 50818@debbugs.gnu.org
> Date: Mon, 27 Sep 2021 14:52:15 -0400
> 
> I decide to go ahead with a Cygwin-specific patch (attached).  If Andrea or 
> someone else decides this would be good for all platforms, they can do that 
> later.
> 
> OK to push?

Yes, please.