sync: use XDG_STATE_HOME
sync: use XDG_STATE_HOME

XDG_RUNTIME_DIR is systemd-specific and may not be available under
certain conditions, e.g. when the user is not logged in. Switch to
XDG_STATE_HOME which is in $HOME and can always be created, unlike
directories in /run/user.

Fixes https://github.com/alexheretic/aurto/issues/76

AladW/aurutils,AladW/aurutils