It looks like fd 3 needs to be closed IN ADDITION to STDIN/STDOUT/STDERR for `direnv` to return control to the user.
By closing fd 3 after we `fork` but before we `exec` `redis-server` and `mariadbd`, we can ensure that they don't cause `direnv` to hang.
Kind of annoying, but `direnv` is not designed to handle launching of daemons.. and we're doing some custom stuff instead of `launchd`.