DynamicModule SDK library path

Hello, I would just like to confirm this consideration

> TODO:
> \- Is $CUDA_ROOT/lib64 the correct path to assume for 64-Bit CUDA libraries on Linux?

in `_locate_cuda_libdir` of the `DynamicModule` class in `compiler.py`

I'm running 64-bit Linux (Ubuntu 20.04) and installed cuda and pycuda in a conda environment. In particular `_locate_cuda_libdir` ends up in this case for me:
```
if libdir is None:
nvcc_path = _find_nvcc_on_path()
if nvcc_path is not None:
libdir = join(os.path.dirname(nvcc_path), "..", "lib64")
```

However the correct directory name is just "lib" instead of "lib64" in my installation. Providing the correct path in the constructor of course makes it work.