[Feature Request] Add test for DXIL shared library Loadability

[pow2clk]

Is your feature request related to a problem? Please describe.

Past releases have included unloadble dxil libraries. These slipped through all testing due to lack of any test that would have caused that unloadability to result in a failure.

Describe the solution you'd like We need to be able to verify that this is possible to load the dxil library for all platforms. For this, we need a variant of the validation test that forces a loading of the external library and fails if it can't be done.