Fix writing XDG_CONFIG_HOME in test-bundler
https://github.com/ruby/actions/actions/runs/756591173
Errno::EACCES: Permission denied @ dir_s_mkdir - /home/runner/.config/irb
Fix writing XDG_CONFIG_HOME in test-bundler
https://github.com/ruby/actions/actions/runs/756591173