[WIP] Fix MSVC Python compilation detection

PYTHON_WORKING_DIR must be the same binary location as specified for try_compile, else we get this error:

Reason: An error occurred while running a small Boost Python test project.

we encountered this while building for conda: https://github.com/conda-forge/staged-recipes/pull/1251

Also this is more a detail but I dont see why CMAKE_BUILD_TYPE couldn't be set by default for win32 too.