People seem to get bit fairly often, in various ways, by stale pkgsrc 
work dirs. What's the purpose of leaving ${WRKDIR} around after, e.g., 
"install" or "package"? What would be the drawbacks of automatically 
"clean"ing, by default, after user-oriented targets? Of course, we'd 
want to avoid auto-cleaning if PKG_DEVELOPER is set.

Comments? What haven't I thought about?

- Amitai