Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.

Use `jt ruby-home` instead of `mx standalone-home`

* The latter no longer works with unchained standalones.