Stuff that isn't permanant, but is near-necessary to build the thing.
Analagous to jigs in a woodshop or scafolding on a constructions site. Or
survey pegs in sitework. Or ...

Stuff that may be useful during development that doesn't want to be in a
"finished product".

spam256 takes 15 minutes to aq 256k of crap. On a P166. So Linux would
take an hour, plus or minus half a decimal order of magnitude. aq doesn't
have the state-capacity issues things like branch-resolution have.
Something like a Linux might exhaust the shell, but then, check out those
Linux config.config.makeconfig scripts.

