blt_cuda_smoke compiled with default arch

[cyrush]

I noticed that blt_cuda_smoke is built with default arch, while most of the code I want to test is built with extra arch flags.

That can lead to a blt_cuda_smoke that works when other exes do not.

This is a BLT usage thing we should make folks aware of.

[adayton1]

This is somewhat related, but with CMake 3.21.1, I get a warning regarding the cuda smoke test:

CMake Warning (dev) in cmake/blt/tests/smoke/CMakeLists.txt:
  Policy CMP0104 is not set: CMAKE_CUDA_ARCHITECTURES now detected for NVCC,
  empty CUDA_ARCHITECTURES not allowed.  Run "cmake --help-policy CMP0104"
  for policy details.  Use the cmake_policy command to set the policy and
  suppress this warning.

  CUDA_ARCHITECTURES is empty for target "blt_cuda_openmp_smoke".
This warning is for project developers.  Use -Wno-dev to suppress it.

[white238]

This is something we should not be setting directly in BLT because it is platform specific. Most projects have this in their generated host-configs:

set(CMAKE_CUDA_ARCHITECTURES "70" CACHE STRING "")

[white238]

This CMake property was added in CMake 3.18 https://cmake.org/cmake/help/git-stage/variable/CMAKE_CUDA_ARCHITECTURES.html