launcher: warn when verification is disabled

Make it clear(er) to the user that this option is dangerous.

Bug: https://crbug.com/gerrit/11045
Change-Id: I5580996c26653a7c823b69008de3626abf1b0068
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/257333


Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: David Pursehouse <dpursehouse@collab.net>