message: COMP: silence compiler warnings due to unused vars
  Depending on the build configuration, some constexpr variables
  may not be used leading to compiler warnings. Fixed that.
diff: @@ -302,11 +302,9 @@ TEST( core_memory_management, set_get_default_memory_space )
  //------------------------------------------------------------------------------
  TEST( core_memory_management, alloc_free )
  {
  +#ifdef AXOM_USE_UMPIRE
  constexpr bool HOST_ACCESSIBLE = true;
  - constexpr bool NOT_HOST_ACCESSIBLE = false;
  -
  -#ifdef AXOM_USE_UMPIRE
  const int HostAllocatorID =
  axom::getResourceAllocatorID( umpire::resource::Host );
  @@ -316,6 +314,8 @@ TEST( core_memory_management, alloc_free )
  #ifdef AXOM_USE_CUDA
  + constexpr bool NOT_HOST_ACCESSIBLE = false;
  +
  const int PinnedAllocatorID =
  axom::getResourceAllocatorID( umpire::resource::Pinned );
  check_alloc_and_free( axom::getAllocator( PinnedAllocatorID ),
  @@ -349,17 +349,18 @@ TEST( core_memory_management, alloc_free )
  //------------------------------------------------------------------------------
  TEST( core_memory_management, alloc_realloc_free )
  {
  - constexpr bool HOST_ACCESSIBLE = true;
  - constexpr bool NOT_HOST_ACCESSIBLE = false;
  -
  #ifdef AXOM_USE_UMPIRE
  + constexpr bool HOST_ACCESSIBLE = true;
  +
  check_alloc_realloc_free( axom::getAllocator( umpire::resource::Host ),
  HOST_ACCESSIBLE
  );
  #ifdef AXOM_USE_CUDA
  + constexpr bool NOT_HOST_ACCESSIBLE = false;
  +
  const int PinnedAllocatorID =
  axom::getResourceAllocatorID( umpire::resource::Pinned );
  check_alloc_realloc_free( axom::getAllocator( PinnedAllocatorID ),
  