Add i.MX6's toolchain into CI Ubuntus

Only installs on Ubuntu 12.04 x64.
Change-Id: I3d6f574cf05af18db074b869eccfeac3637cab57
Reviewed-by: Simo Fält <simo.falt@digia.com>
Reviewed-by: Heikki Halmet <heikki.halmet@digia.com>