[Rock-dev] Checking out autoproj and autobuild by default on master

[Sylvain Joyeux]

> Anyway, is there a reason why you install autoproj as gem in the first
> place? I really like the approach form homebrew here (everything is a git).
Chicken and egg. One needs autoproj to checkout autoproj. The
bootstrap script is stripped down to osdep support so that it can
install the gem and then properly bootstrap.

Sylvain