Expose option to build shared libs in root CMakeLists.txt

- fixes linker errors in windows CI and warnings on linux/mac.
- this line was previously in `vtkMobileDevices.cmake` and it executed on non-mobile devices. It was yanked in vtk/vtk!11510 which caused `BUILD_SHARED_LIBS` to never be set!

CMakeLists.txt

@@ -122,6 +122,8 @@ if (NOT CMAKE_INSTALL_QMLDIR)
     "${CMAKE_INSTALL_LIBDIR}/qml")
 endif ()
 
+# Choose static or shared libraries.
+option(BUILD_SHARED_LIBS "Build VTK with shared libraries." ON)
 set(VTK_BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS})
 set(CMAKE_CXX_VISIBILITY_PRESET "hidden")
 set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)