Evaluate glslang for HLSL->SPIR-V

[maluoi]

Glslang theoretically can also compile HLSL to SPIR-V. It claims to be a partial implementation, but the list looks pretty complete to me!

Glslang also happens to be smaller, and significantly easier to build/use as a dependency. If the output it generates is usable by StereoKit, I'd take it in a heartbeat!