Restore pre command

Author: remia

share/cmake/macros/GetPythonPreCommand.cmake

@@ -66,7 +66,7 @@ macro(get_python_pre_command)
         # on Windows with:
         #   '> set PYTHONPATH=XXX \n call CMD'
         # '\n' is here because '\\&' does not work.
-        set(Python_PRE_CMD set ${_PATH_SET} "\n" call)
+        set(Python_PRE_CMD set ${_PATH_SET} "\n" set ${_PYTHONPATH_SET} "\n" call)
 
         message(STATUS "Python pre-command: ${Python_PRE_CMD}")