IOSS build failure

This relates to Topic update-ioss, MR !10879 (merged).

@spiros.tsalikis

The build fails in Windows and Linux. I am using the latest Visual Studio (17.10.3) and gcc (Ubuntu 13.2.0-23ubuntu4) 13.2.0, Qt is is version 6.7.2.

I also see the same error happening here: https://open.cdash.org/viewBuildError.php?buildid=9736909

The error is this:

FAILED: ThirdParty/ioss/vtkioss/CMakeFiles/ioss.dir/Ioss_Property.C.o 

...

In file included from /<user>/vtk/ThirdParty/ioss/vtkioss/Ioss_Property.C:9:
/home/amaclean/Kitware/vtk/vtk/ThirdParty/ioss/vtkioss/Ioss_Property.C: In member function ‘bool vtkioss_Ioss::Property::get_value(int64_t*) const’:
/<user>/vtk/ThirdParty/ioss/vtkioss/Ioss_Property.C:357:17: error: ‘holds_alternative’ is not a member of ‘std’
  357 |     assert(std::holds_alternative<int64_t>(data_));
      |                 ^~~~~~~~~~~~~~~~~
/<user>/vtk/ThirdParty/ioss/vtkioss/Ioss_Property.C:357:17: note: ‘std::holds_alternative’ is only available from C++17 onwards

I thought VTK was already using C++17 so I'm not sure what is going on here.