They have to be rolled simultaneously due to a breaking change.

https://swiftshader.googlesource.com/SwiftShader.git/+log/214ec337a0b2..da659b374113
https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git/+log/79f8caf9154a..8910ea5f1c7b

Bug: angleproject:4425
Change-Id: If9b402295375436fcdb344835b65be7d2b55abc7
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2071011
Commit-Queue: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>