Currently, running any task while attached to elasticsearch will also
try to run that task in all elasticsearch projects. This change causes
x-plugins to be moved into a subproject when attached. It does this by
dynamically creating a fake root project, and making this root project
think it is attached to the existing attachments, along with x-plugins
itself.
This also fixes buildSrc so attachment to elasticsearch's buildSrc
actually works.
Original commit: elastic/x-pack-elasticsearch@da0adf1da5
Ryan Ernst