[3dprinter-general] Bug#900425: protobuf 3.5.2 transition and cura-engine

[Gregor Riepl]

Hi,

Thanks for the advance notice.

CuraEngine depends on libArcus, which also links against protobuf, so it's not
sufficient to just recompile CuraEngine.

I'm going to try a test rebuild of libArcus and CuraEngine with protobuf from
experimental to check if it's ready for the transition, but it's important to
make sure _both_ packages are updated. Is there a good way to make sure
libArcus is rebuilt first?

We have a new release in the pipeline anyway, but it needs to be uploaded by a
DD. Should I follow your advice and set the minimum version before the upload?