Header test builds for PPP2 are causing visual studio compiler errors

For some reason, the header test builds in the subdirectories of vtkm/worklet/contourtree_augmented/mesh_dem_meshtypes are causing compiler errors like this:

vtkm\worklet\contourtree_augmented\mesh_dem_meshtypes\freudenthal_3D\TB_ExecutionObject_MeshStructure_h.cxx: fatal error C1041: cannot open program database 'vtkm\worklet\contourtree_augmented\mesh_dem_meshtypes\freudenthal_3D\CMakeFiles\TestBuild_vtkm_worklet_contourtree_augmented_mesh_dem_meshtypes_freudenthal_3D.dir\TestBuild_vtkm_worklet_contourtree_augmented_mesh_dem_meshtypes_freudenthal_3D.pdb'; if multiple CL.EXE write to the same .PDB file, please use /FS

These can be seen in errors on the dashboard like this: https://open.cdash.org/viewBuildError.php?buildid=5560514

There is a temporary workaround in MR !1428 (merged) that disables the header test builds that are causing problems. However, someone should identify the real cause of the issue and fix it.