Turns on Tint generation of SPIR-V if UseTintGenerator is on.
This affects SPIR-V generation for Vulkan, and SPIR-V passed
into SPIRV-Cross to produce GLSL.
It enables DrawTests use_tint_generator for Vulkan/GL where it
should have at least basic support.
Bug: dawn:571
Change-Id: I5df1435bee17572259f5aa3605c4bf19c0136cbc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/32302
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>