MSVC_RUNTIME_LIBRARY target property should not be set explicitly

Hi there. I'm running into problems with the following statement:
https://github.com/AcademySoftwareFoundation/openvdb/blob/73de06e50852f6bf70d1523558bb1f9c929fedf5/openvdb/openvdb/CMakeLists.txt#L516

Choosing to link against static or dynamic MSVC runtime has nothing to do with whether to link against a static or dynamic version of OpenVDB. The statement above is problematic in situations where other third-party libraries have been defined beforehand, and initialized to compile with `/MD`, but then we pull OpenVDB, which imposes `/MT`, and final linking fails. CMake configuration should still work when one leaves a default, unspecified value for `CMAKE_MSVC_RUNTIME_LIBRARY`, so I would suggest to remove this line, or make it a controllable CMake option.

Start at openvdb/openvdb/CMakeLists.txt around line 516 and review how MSVC_RUNTIME_LIBRARY is set relative to CMAKE_MSVC_RUNTIME_LIBRARY. Check the CMake configuration with an unspecified default and with third-party libraries using /MD; done means OpenVDB no longer overrides that choice or causes the conflicting runtime flags described in the issue.

Written by the indexing model from the issue text.