Re: Only expose final results

[Chris Warburton]

We've now moved some of the cache-generation code out of
pseudo-standalone scripts and into Nix builders (using our own
'runRacket' function, rather than the bash-based 'runCommand').

It doesn't seem to make sense having tests in these derivations, so
instead we've just moved across anything that's *only* used by the data
generation, and we leave behind things which are used elsewhere (either
by other code, or by tests).

There's still room for some more cleaning up, so I'll leave this open.