-current broken when src is on NFS

[Simon J. Gerraty]

> Given that we have (or at least had at one time) some of those magical
> "..." paths that cause bmake to search up the hierarchy for its .mk
> files, I wonder if an odd relationship between src and obj dir confuses
> it, or if it somehow wanders into a wrong src tree while searching?

Based on Daniel's latest mail, the issue would appear to be the way he
was setting MAKEOBJDIRPREFIX.

As for .../ src.sys.env.mk resolves that to absolute path
since otherwise things like kernel builds wouldn't work - make run from
within obj tree.