Solved by tom in post #2 
              
              
                So I use the AMD-provided deb repository from the AMD. Obviously, I am prone to using this recipe for building. 
From the error message, you probably don’t have a full rocm installation.  For me, the clang is in the llvm-amdgpu package: 
$ dpkg -S /opt/rocm-4.0.0/llvm/bin/clang++ 
llvm-amdgpu: /opt/…