Actually you don't need SPARC hardware to build sparc64 userland:
qemu-system-sparc64 boots Linux and may be fast enough for building stuff.
It is limited to one CPU, but I guess a fast PC running qemu is
consuming less electricity than an old sun4u machine.

Hey wow, that's a great alternative for at home indeed, thanks for that.
I tried to install the 12 Beta on a T2000 today (which is not at home ;-)). and it panics during the kernel boot.
But Solaris 11 panics too with messages like "Exception handler interrupted, please file a bug", so I guess I first have to upgrade the firmware on this thing. (Which wouldn't surprise me judging by what I get to work with).

More will follow soon.

Patrick