message: ENH: set correct CUDA_ARCH in generated hostconfig
  Set CUDA_ARCH according to the platform, i.e., 'sm_60' on
  rzmanta and 'sm_70' on rzansel.
diff: @@ -142,6 +142,7 @@ class UberenvAxom(Package):
  # are we on a specific machine
  on_bgq = 'bgq' in sys_type
  on_blueos = 'blueos' in sys_type
  + on_blueos_p9 = 'p9' in sys_type
  on_toss = 'toss_3' in sys_type
  # cmake
  @@ -414,9 +415,14 @@ class UberenvAxom(Package):
  cfg.write("##############\n\n")
  cfg.write(cmake_cache_option("ENABLE_CUDA", True))
  - cfg.write(cmake_cache_entry("CUDA_TOOLKIT_ROOT_DIR", "/usr/tce/packages/cuda/cuda-9.2.148"))
  + cfg.write(cmake_cache_entry("CUDA_TOOLKIT_ROOT_DIR", "/usr/tce/packages/cuda/cuda-10.1.168"))
  cfg.write(cmake_cache_entry("CMAKE_CUDA_COMPILER", "${CUDA_TOOLKIT_ROOT_DIR}/bin/nvcc"))
  +
  + if on_blueos_p9:
  + cfg.write(cmake_cache_entry("CUDA_ARCH", "sm_70"))
  + else:
  cfg.write(cmake_cache_entry("CUDA_ARCH", "sm_60"))
  +
  cfg.write(cmake_cache_entry("CMAKE_CUDA_FLAGS" ,"-restrict -arch ${CUDA_ARCH} -std=c++11 --expt-extended-lambda -G"))
  if "+mpi" in spec:
  