[BUILD] unresolved external symbol involving half

`1>VDB_Test.cpp.obj : error LNK2019: unresolved external symbol "private: static short __cdecl openvdb::v9_1::math::internal::half::convert(int)" (?convert@half@internal@math@v9_1@openvdb@@CAFH@Z) referenced in function "float __cdecl openvdb::v9_1::io::truncateRealToHalf(float const &)" (??$truncateRealToHalf@M@io@v9_1@openvdb@@YAMAEBM@Z)

1>VDB_Test.gen.cpp.obj : error LNK2001: unresolved external symbol "private: static short __cdecl openvdb::v9_1::math::internal::half::convert(int)" (?convert@half@internal@math@v9_1@openvdb@@CAFH@Z)`

I get these in addition many other errors concerning the internal half type. I am using visual studio.

Start by reproducing the Visual Studio linker errors involving VDB_Test.cpp.obj and VDB_Test.gen.cpp.obj, then trace references to openvdb::v9_1::math::internal::half::convert(int) and truncateRealToHalf. Compare the unresolved symbol with the available half implementation and build configuration; done means the test objects link without the half-related errors.

Written by the indexing model from the issue text.