During the build of conntrack-tools we need to first install the recent version
of libnetfilter-conntrack-dev build in a previous step as its a dependency.
Instead of writing the same code over and over again, place the common parts
into a Jenkins Library which is then consumed by every individual build Job.
This not only makes it less complex, but also increases maintainability by
several magnitudes.
Instead of scattering build instructions accross individual repositories for
some additional packages we want to build from latest Debian releases, this
is a proof-of-concept how to integrate an individual package Pipeline into the
overall VyOS build repository.
A dedicated Jenkins job will be required for this Pipeline but it will only
compile if files are actually changes in the directory path relevant for
this components.
