[tlbuild] trial builds for TL'13

[Karl Berry]

Thomas reports (and Mojca did too):

    There is a new dependency on automake, 
    [... cairo failure ...]

There is not supposed to be any such dependency!!  As soon as automake
is run, it's highly unlikely that anything will work.  Going down that
path is not what's desired, not at all, not in any way.

A clean checkout or rsync (anything preserving timestamps) is not
supposed to induce any automakery.  I'll see if I can figure out what
madness in cairo is causing this.  Argh.

karl