Fixing this issue required using the WrapOpKill SPIRV-Tools
pass. This pass wraps OpKill instructions inside a function.
See the following for the explanation:
https://github.com/KhronosGroup/SPIRV-Tools/issues/2726

dEQP-GLES2.functional.shaders.discard.function_always fails
on ANGLE on top of SwiftShader Vulkan without this fix.

Bug b/141246700

Change-Id: I48ce3c19a1b02160fd8f23b60a75e5f8f35a4d37
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36450
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>