message: try out OSPAny, seems to work
diff: // ospcommon
  #include "ospcommon/vec.h"
  +#define USE_OSPANY 1
  +
  +#if USE_OSPANY
  +# include "sg/common/OSPAny.h"
  +#else
  # include "sg/common/OSPVariant.h"
  +#endif
  #include <mutex>
  namespace ospray {
  namespace sg {
  +#if USE_OSPANY
  + using SGVar = OSPAny;
  +#else
  using SGVar = OSPVariant;
  +#endif
  /*! forward decl of entity that nodes can write to when writing XML files */
  struct XMLWriter;
  