Does anyone know of any current implementation of toolchain changes
which would allow to distribute compilation among a cluster of
networked machines?

I have seem distcc utility, which seems useful in that area, however
this seems to assume that the same compiler setup exists on all
involved systems. Moreover, because of the nbmake wrapper, I am unsure
if this could be used to compile netbsd systems.

Since NetBSD is well known for it's excellent support for
cross-compiling on various host OSs and for arbtrary target
architectures, using a common framework in the toolchain, perhaps that
such support for clusters might be desireable. Even the releng process
could possibly be helped by such setups...

If there exists such solutions already, I would be glad to know about them

Thanks,
Matthew Mondor