This brings separate initialization for libcuda and libnvrtc, which
fixes Cycles nvrtc compilation not working on build machines without
CUDA hardware available.
Differential Revision: https://developer.blender.org/D3045
nvcc is very picky regarding compiler versions, severely limiting the compiler we can use, this commit adds a nvrtc based compiler that'll allow us to build the cubins even if the host compiler is unsupported. for details see D2913.
Differential Revision: http://developer.blender.org/D2913