Vulkan: add autogen dependency to shader variations files Bug: angleproject:3432 Change-Id: If16e5264d539c6a3944a60f4d28f4e6aa5420fe3 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2235353 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>