Use Ubuntu 14.04. It is old but still supported so you can install old catalyst which have OpenCL 2.0 support. AMDGPU-PRO is still in development and beta status.
Hmm... I there any way to get Catalyst to work on 16.04? It might be better if I could compile my code with new compiler and libraries.
Just some rambling. Why AMD discarded catalyst while AMDGPU is still in beta. That's a super bad decision for a developer.
Anyone have any idea on when OpenCL 2.0 support will land on AMDGPU-PRO? I'm looking forward to it.