tests/shader_runner: Query for GLSL target support instead of checking VKD3D_SHADER_UNSUPPORTED_GLSL.
tests/shader-runner: Query for SM6 support instead of checking VKD3D_SHADER_UNSUPPORTED_DXIL. This change avoids skipping the tests on a Windows build, where the support is present but the macro is not defined. Thanks Giovanni for pointing this out.