stub: try to avoid have ; replace by list separator (5th try)

stubs.cmake

@@ -102,29 +102,29 @@ function(GENERATE_STUBS module_path module_name module_install_dir)
   set(ENV_PATH)
   set(optional_args ${ARGN})
   if(WIN32)
-    # Ton of conflict between path separators, cmake lists separator and
-    # generator expression
     foreach(py_target IN LISTS optional_args)
       if(TARGET ${py_target})
         set(_is_lib
             "$<STREQUAL:$<TARGET_PROPERTY:${py_target},TYPE>,SHARED_LIBRARY>")
         set(_target_dir "$<TARGET_FILE_DIR:${py_target}>")
-        set(_target_path "$<${_is_lib}:${_target_dir}>@${_target_path}")
+        set(_target_path $<${_is_lib}:${_target_dir}> ${_target_path})
       endif()
     endforeach()
-    string(REPLACE ";" "@" _path_cmake $ENV{PATH})
-    set(_path_cmake "${_target_path}${_path_cmake}")
-    string(REPLACE "@" "\\\;" _path_str ${_path_cmake})
-    set(ENV_PATH "PATH=${_path_str}")
+    set(_path_native $ENV{PATH})
+    file(TO_CMAKE_PATH "${_path_native}" _path_cmake)
+    set(_path_cmake ${_target_path} ${_path_cmake})
+    # TODO in cmake 3.12 :(
+    list(JOIN _path_cmake "\\\;" _path_cmake)
+    set(ENV_PATH PATH=${_path_cmake})
   endif()
 
   add_custom_target(
     ${target_name} ALL
     COMMAND
-      ${CMAKE_COMMAND} -E env PYTHONPATH=${PYTHONPATH} ${ENV_PATH}
-      "${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 ${ENV_PATH} ${CMAKE_COMMAND} -E env
+      PYTHONPATH=${PYTHONPATH} "${PYTHON_EXECUTABLE}" "${STUBGEN_MAIN_FILE}"
+      "-o" "${module_path}" "${module_name}" "--boost-python" --ignore-invalid
+      signature "--no-setup-py" "--root-module-suffix" ""
     VERBATIM)
   foreach(py_target IN LISTS optional_args)
     if(TARGET ${py_target})