Build a shared library on windows with MSVC

[php1ic]

The cmake config currently builds a static library on windows when MSVC is used. I tried to keep it generic and OS agnostic, but ran into issues with dll and lib files when it came to linking the final test binary.

If someone needs a shared library for windows/MSVC use then I will need some help with how to set things up to build a file that can be linked.

I tried the advice given in
https://stackoverflow.com/questions/26495564/why-is-my-shared-library-not-linking-correctly-when-using-cmake
and
https://stackoverflow.com/questions/33062728/cmake-link-shared-library-on-windows
but neither worked.