GNAT version does not support Ada-2012 standard. Would be good to have the same version of gcc as the system base (currently 4.6.2) or 4.7.0
Why is Ada not supported by a use flag like fortran?
need gnat-gcc >= 4.6 for SPARK support.
I just commited 4.6.4 (better late than never ;)
Have at it...