clang/7+cuda/9 build -Werror-unused parameter error in nightly test

[ndellingwood]

Sample error:

18:48:10 /home/jenkins/slave/workspace/Kokkos_develop_kokkos-dev_clang_701_cuda_92/kokkos/core/src/impl/Kokkos_Atomic_Load.hpp:123:8: error: unused parameter 'ptr' [-Werror,-Wunused-parameter]
18:48:10     T* ptr, typename std::enable_if<!(sizeof(T) == 1 || sizeof(T) == 2 ||
18:48:10        ^
18:48:10 1 error generated when compiling for sm_35.

Sample reproducer:

   #   Load modules:
         module load sems-env sems-cmake/3.12.2 kokkos-env kokkos-hwloc/1.10.1/base sems-clang/7.0.1 sems-cuda/9.2
 
   #   Use generate_makefile line below to call cmake which generates makefile for this build:
         /home/jenkins/slave/workspace/Kokkos_develop_kokkos-dev_clang_701_cuda_92/kokkos/generate_makefile.bash --with-devices=Cuda,OpenMP --arch=Kepler35 --compiler=/projects/sems/install/rhel6-x86_64/sems/compiler/clang/7.0.1/base/bin/clang++ --cxxflags="-O3 -Wall -Wunused-parameter -Wshadow -pedantic -Werror -Wsign-compare -Wtype-limits -Wuninitialized " --cxxstandard="11" --ldflags="" --with-cuda=/projects/sems/install/rhel6-x86_64/sems/compiler/cuda/9.2/base --kokkos-path=/home/jenkins/slave/workspace/Kokkos_develop_kokkos-dev_clang_701_cuda_92/kokkos --no-examples 

[crtrott]

Ok this only happens for Kepler class GPUs.