Vulkan: Fix build after roll. Remove struct_size_helper from LVL build. This was causing significant problems on the Chromium CQ. Also fix the warning of duplicate definitions in reg.py by staging scripts to a temporary folder so we can use a fixed version. Bug: angleproject:2482 Bug: chromium:833736 Change-Id: Ide7202fe14bf6c83419f19bc07113df23d51807a Reviewed-on: https://chromium-review.googlesource.com/1014902 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>