Fix gitaly-ruby not starting on test

gitaly-ruby added logging in
https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2678, but by
default it will save the file in /. To avoid crashing, save it inside
the Rails log directory.

The Gitaly default dir will be adjusted in
https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2678.

lib/gitlab/setup_helper.rb

@@ -99,6 +99,7 @@ module Gitlab
           config[:'gitlab-shell'] = { dir: Gitlab.config.gitlab_shell.path }
           config[:bin_dir] = Gitlab.config.gitaly.client_path
           config[:gitlab] = { url: Gitlab.config.gitlab.url }
+          config[:logging] = { dir: Rails.root.join('log').to_s }
 
           TomlRB.dump(config)
         end