[tlbuild] initial test builds for TL'15 (no commits)

[Karl Berry]

Hi Thomas - glad the build worked.

I don't know of anyone else with powerpc-linux.  As long as
you can and want to build the binaries, I'm happy to include them, but
when you can't, I expect they will just be dropped.  If you want to drop
them now, I'm fine with that too.  I have no way to know how many users
there are, or if there are any at all.

Thanks,
Karl