This is in anticipation of running manage-projects, which wants to
use the dev subdir of project-config when run on dev, but we're
currently not doing anything with that. Point at root or dev as
appropriate. Then we can do a similar thing - probably just
bind-mounting the root or the dev when we docker run for
manage-projects.
Change-Id: Ia13bbb0bf8dbe1f7e7c0f378ba9b41bef3ecd5c1