Comment # 3 on bug 1227304 from huakim tylyktar

(In reply to Adrian Schröter from comment #2)
> yes, it is too late to do that at build time. The VM has no network and the
> dependencies can not pre-calculated.
> 
> Either do that in default mode, so the change gets commited to the source.
> 
> Alternative is to use dynamic build dependency implementation where another
> build job gets started in case dependencies are changing. That is a generic
> rpm feature, supported by OBS by respawning a new job.
> https://fedoraproject.org/wiki/Changes/DynamicBuildRequires
> 
> 
> closing as works as designed.

But, maybe, we just need to add the feauture to order to respawn a new job
before rpmbuild?