Support using nvc++ as the CUDA host compiler / compiler for host c++ under linux, via CMake.

Will require:

• Warning changes
• Prevention of building swig with nvc++ (likely)
• Patching rapidjson etc. See NVHPC Support #693

When using CMake 3.21 and nvhpc 21.7 with nvc++ as the host compiler, rapidjson cannot be compiled due to use of uint128. This needs further investigation, as the section of code was macro guarded behind some gcc specific looking macros.

Unlear if this version would work when using nvcc from the nvhpc install, but using g++ as the host compiler (the above issue re: curand).

Additionally, #661 makes use of findCUDAToolkit which may also improve the situiation (if findCUDAToolkit is nvhpc compatible/aware)

This has been split out from #563