message: BUGFIX: anonymous struct inside union breaks PGI
  Fixes issue when compiling with the PGI compiler and CMake 3.9.
  CMake 3.9 emits the "-A" flag which causes errors with non-ANSI
  conforming code.
diff: @@ -163,12 +163,14 @@ int STLReader::readBinarySTL()
  union BinarySTLTri
  {
  common::int8 raw[BINARY_TRI_SIZE];
  +
  struct
  {
  float normal[3];
  float vert[9];
  common::uint16 attr;
  - };
  + } data ;
  +
  } tri;
  bool const isLittleEndian = axom::utilities::isLittleEndian();
  @@ -202,7 +204,7 @@ int STLReader::readBinarySTL()
  for(int j=0 ; j<9 ; ++j)
  {
  float coord = isLittleEndian ?
  - tri.vert[j] : utilities::swapEndian(tri.vert[j]);
  + tri.data.vert[ j ] : utilities::swapEndian( tri.data.vert[ j ] );
  m_nodes.push_back( static_cast<double>( coord) );
  }
  