PCL was already defaulted to OFF on Linux, this changes the default to OFF on MSVC
as well. This can be reverted once the primary LibPack for Windows includes a version
of FLANN that compiles under C++17 (the last official release of FLANN, 1.9.1, does
not, but the HEAD in their Git repository does).
If INSTALL_TO_SITEPACKAGES is enabled, the freecad-namespace package (freecad/__init__.py) is installed in the python-sitepackage-dir. Further, the library install path (CMAKE_INSTALL_LIBDIR)
is used to find the FreeCAD shared library. If, for some reason, one wants to import another installed FreeCAD version it's possible to set the environment variable "PATH_TO_FREECAD_LIBDIR" to
point to the wanted FreeCAD-library (FreeCAD.so / FreeCAD.dll)
