What are we trying to do here, exactly?
Yes it is for tests added later. I've deleted it from this series. We will need a means to add the signature for the tests.
For the d3d12 and shader runner tests I've been using an environment variable to specify the path to DXC, HLSL source declarations in d3d12.c, and an `[enable]` directive in shader runner. Are those acceptable for upstream?