Build system race conditions

[Martin Husemann <martin%duskware.de@localhost>]

Folks,

we have some annoying fallout from every build now on the releng autobuild
cluster after it has been speed up quite a bit.

The issues are generic, random race conditions in the NetBSD build system
and not related to anything special on the autobuild machines (besides those
building often and very fast).

This failures make it hard to spot real bugs breaking some ports, and it would
be very, very cool to have thme shake out, so at least the release branches
would provide consistent 0-failure builds on the releng cluster.

You can see the releng build results here:

        http://releng.netbsd.org/cgi-bin/builds.cgi

and the ideal rendering should be all green and black in the last two columns.

Any help/hints greatly appreciated!

Martin