Running `guix archive --authorize` sets /etc/guix/acl to 600
via with-atomic-file-output via mkstemp!.
Then running `guix substitute --help/--version` fails on "permission denied".
While "guix substitute" is an internal tool, the options --help and --version
exist and you should be able to run those from the command line.
* guix/scripts/substitute.scm (guix-substitute): Earlier check for
--help or --version.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>