[Anthill-pro] old buildlife code on agent disk

[Michael Feinberg]

 > Your confusing incremental compilation with a clean workspace.

Not really. I have seen cases where people output auto-generated code 
right into the source tree and then do not structure the dependency 
right so that things get cleaned up and regenerated  properly. Only true 
"clean" builds can detect things like that. I choose not to care about 
extra few mins it takes to cech out the code.