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

[Karl Berry]

    > Is there a way to tell Build to run all the tests, even if one fails?

When the goal is just to report the failed test and then see if there
are any further failures, you could temporarily cp /bin/true to the
failed test script.  It'd get re-updated to normal with the next sync
from source.

thanks,
k