VVL: Add new GN override for spirv Fixes the following vulkan-deps roll: https://chromium-review.googlesource.com/c/angle/angle/+/3895572/ Bug: angleproject:7658 Change-Id: Ic5acc1bbee8a064b2b06adf2ad42e1213d8c901e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3895532 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>