Friction points for CI

[cwpearson]

Some pain points kept #101 from being comprehensive:

• virtualfunction needs a separate CUDA-enabled Kokkos build with RDC enabled
• Not all exercises use CMake
• Not all exercises have the same structure (e.g. no Begin / Solution subdirectories)
• Some exercises hard-code specific execution spaces (purposefully or otherwise)
• Some exercises need additional libraries
  • Kokkos Kernels (okay, slow-ish to build)
  • Kokkos remote spaces
• Some exercises use Kokkos Kernels implementation details (testing utility functions)
• Some exercises use deprecated interfaces (tasking?)