[CMake] protobuf and imports relative to root (and --proto_path)

[Alexander Neundorf]

On 2018 M09 25, Tue 16:53:27 CEST David Jobet wrote:
> > What I do have a problem is rerunning protoc automatically on proto-files
> > which import proto files that have been modified.
> > How do you handle this ?
> 
> I just found out I don't.
> Any idea on that one ?

here are some suggestions:
https://cmake.org/pipermail/cmake-developers/2018-May/030664.html

Alex