new pbulk feature: package build priorities

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

Thanks to joerg, pbulk (starting from pbulk-base version 0.56) now has
support for prioritizing packages in the build order.

For this ordering, the variable PBULK_WEIGHT is used. The default
value (if none is set) is 100, higher numbers mean that the package
will be built earlier. (Lower numbers and even negative ones are also
possible.)

This helps with the problem that bulk builds often end building heavy
packages with lots of dependencies last, so that the parallelization
provided by multiple pbulk clients can not be used optimally.

As an example of how to use this, you can add the following to your
/etc/mk.conf file:

.if !empty(PKGPATH:Mmisc/libreoffice)
PBULK_WEIGHT=  1000000
.endif

This will build libreoffice (and its dependencies) as early as
possible.

Give it a try!
 Thomas