bug#23451: 25.0.93; Clarify the dependency on find/grep for platforms not having those tools

[Eli Zaretskii]

> Cc: 23451@debbugs.gnu.org, kaushal.modi@gmail.com
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 30 May 2017 01:00:18 +0300
> 
> On 5/29/17 8:35 PM, Eli Zaretskii wrote:
> 
> > I think we should simply test explicitly for 'find' and 'grep' being
> > available, before we run the command.
> 
> Windows comes with find.exe, though, one we can't use.

Yes, I meant to test it's the find we expect, not the one which comes
with Windows out of the box.  Which means not just executable-find,
but something a bit more sophisticated.