Summit user guide typo for nvcc host compiler selection (-ccbin)

[dpuleri]

In the Summit user guide section on compilers the snippet for changing the nvcc host compiler location is incorrect. It is written as --ccbin when it should be -ccbin with one hyphen.

Here are the nvidia docs on the same topic: https://docs.nvidia.com/cuda/cuda-compiler-driver-nvcc/index.html#file-and-path-specifications-compiler-bindir.