VxWorks: Add Platform ID for Modules/CMakePlatformId.h.in

I ever created a merge request to Add VxWorks support (!4636 (closed)), @brad.king kindness told me that I didn't need to do that, CMAKE_CURRENT_LIST_DIR could help our add more module to cmake.

For PLATFORM_ID, I don't know how to handle this out of box cmake, so create this pull request

Backport: release
Topic-rename: VxWorks-platform-id