t/cli.t calls scripts which run with the first perl found in the
user's PATH (usually the system perl), not with the perl used for the
build, as reported here:
https://rt.cpan.org/Ticket/Display.html?id=129944
Thanks to Slaven Rezic for spotting this and reporting it!
Unlike the other tests, this actually treats stow(1) as a black box
script, running it directly rather than require-ing it as a library.
This allows us to check things like the exit codes returned.
