Reduce binary size by pruning CUFFT before linking
Reduce binary size by pruning CUFFT before linking

- Uses nvprune utility to remove unneeded CUDA archs from
  libcufft_static.a.
- This reduces the size of libbifrost.so by roughly half.
- The pruning requires some effort in the Makefile to ensure the
  right CUDA architecture flags are specified.

ledatelescope/bifrost,ledatelescope/bifrost,ledatelescope/bifrost,ledatelescope/bifrost