message: Add device sample run for ex1 on simplices.
  Use the backend specification semmantic `-d ceed-cuda:/gpu/cuda/ref`
  to select a specific backend in libCEED.
diff: // ex1 -pa -d ceed-cpu
  // ex1 -pa -d ceed-cuda
  // ex1 -m ../data/beam-hex.mesh -pa -d cuda
  +// ex1 -m ../data/beam-tet.mesh -pa -d ceed-cuda:/gpu/cuda/ref
  //
  // Description: This example code demonstrates the use of MFEM to define a
  // simple finite element discretization of the Laplace problem
  