stubs: fix PATH issue for Windows

stubs.cmake

@@ -96,13 +96,23 @@ function(GENERATE_STUBS module_path module_name module_install_dir)
     set(PYTHONPATH ${module_path})
   endif($ENV{PYTHONPATH})
 
+  if(WIN32)
+    if($ENV{PYTHONPATH})
+      set(WINDOWS_PATH ${module_path};$ENV{PATH})
+    else()
+      set(WINDOWS_PATH ${module_path})
+    endif()
+
+    set(ENV_WINDOWS_PATH "PATH=${WINDOWS_PATH}")
+  endif(WIN32)
+
   add_custom_target(
     ${target_name} ALL
     COMMAND
-      ${CMAKE_COMMAND} -E env PYTHONPATH=${PYTHONPATH} "${PYTHON_EXECUTABLE}"
-      "${STUBGEN_MAIN_FILE}" "-o" "${module_path}" "${module_name}"
-      "--boost-python" --ignore-invalid signature "--no-setup-py"
-      "--root-module-suffix" ""
+    ${CMAKE_COMMAND} -E env PYTHONPATH=${PYTHONPATH} ${ENV_WINDOWS_PATH} "${PYTHON_EXECUTABLE}"
+    "${STUBGEN_MAIN_FILE}" "-o" "${module_path}" "${module_name}"
+    "--boost-python" --ignore-invalid signature "--no-setup-py"
+    "--root-module-suffix" ""
     VERBATIM)
   set(optional_args ${ARGN})
   foreach(py_target IN LISTS optional_args)