Only link CUDA/OpenCL when needed.
Only link CUDA/OpenCL when needed.


Former-commit-id: ed74f1440df8cb3d6aeb95463c00946f66f46810
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide