Comment 5 for bug 160150

In that case, Upstart cannot work on the OLPC since it must be pid #1 (it's an init daemon).

There is perhaps some small argument for allowing Upstart to run as another pid, but that would necessate disabling features such as supervision of forking daemons, control-alt-delete and alt-uparrow handling, SIGPWR handling, etc.

Since this is a significant functionality reduction, it makes more sense as a compile-time option that a command-line one.