Eli Zaretskii <eliz@gnu.org> writes:

> Actually, I take this back: this defvar will be computed when files.el
> is loaded, which is at dump time.  So this is not TRT, since the
> conditions and the environment at dump time could be very different
> from those at run time.  It could be even on another machine.

Yes, right.  That's no good.

> So I once again suggest to make this a defcustom.  This has two
> advantages:
>
>  . it will be evaluated at Emacs startup, not at dump time

Agreed.  Let's change it into a defcustom.

>  . it will allow users to customize the value and thus avoid costly
>    search  for the program and prevent finding the wrong version of
>    'ls'

Perhaps this part is okay though, given that the search should only
affect users on macOS and *BSD (who presumably will want this anyways)?

Proposed patch attached.