bug#56025: 29.0.50; em-extpipe-test-2 times out on EMBA and Cygwin

[Eli Zaretskii]

> Cc: larsi@gnus.org, 56025@debbugs.gnu.org, spwhitton@email.arizona.edu,
>  kbrown@cornell.edu
> From: Jim Porter <jporterbugs@gmail.com>
> Date: Sat, 25 Jun 2022 09:13:46 -0700
> 
> >>     When [EOF is] received, all the bytes waiting to be read are
> >>     immediately passed to the process without waiting for a <newline>, and
> >>     the EOF is discarded. Thus, if there are no bytes waiting (that is,
> >>     the EOF occurred at the beginning of a line), a byte count of zero
> >>     shall be returned from the read(), representing an end-of-file
> >>     indication.
> > 
> > Perhaps some reference to this should also be in the comments.
> 
> How about this patch? I added a reference to the specific section of the 
> POSIX specification so that it's (hopefully) easy for people to look up 
> if they need further details.

LGTM, thanks.