Bug#861878: nvidia-cuda-toolkit: nvcc needs to pass -fpie to compiler

[Lumin]

@doko GCC-5 may be removed from unstable when CUDA 9.0
is uploaded. See below.
(Maybe doko is already in some of these lists.)

> The problem is the move of some parts of the toolchain to pie by
> default, without updating the whole toolchain. Whenever not using only
> gcc for building object files, the issue shows up. nvcc is only an
> example of this.

Yes, toolchain problem. Due to the difference on the default option,
the mixed use of GCC and CLANG may end up with a failure as shown
in previous examples. This issue is not related to CUDA so I think
another bug against clang should be submitted.

>> And what can we do from the CUDA packaging side except for a new
>> NEWS/README.Debian section?
>>
> That's probably a reasonable thing to do on that side, yes.

The good news is that, the upcoming CUDA 9.0 supports GCC-6
and CLANG-3.9, as reported here

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=862522

That means, the "build your whole application with clang-3.8"
advise is temporary and specific to CUDA 8.0. Before uploading
CUDA 9.0 to unstable/experimental, we can change the default
compiler back to GCC. And backporting CUDA 9.0 to stretch
will eliminate the compiler trouble.