Ensure correct build with no Qt3D installed.
Ensure correct build with no Qt3D installed.

rdebroiz/dtk,NicolasSchnitzler/dtk,d-tk/dtk,d-tk/dtk,d-tk/dtk,rdebroiz/dtk,NicolasSchnitzler/dtk,NicolasSchnitzler/dtk,NicolasSchnitzler/dtk,d-tk/dtk,rdebroiz/dtk,rdebroiz/dtk,d-tk/dtk,d-tk/dtk