HLSL: Add missing BuiltInLayer to HLSL backend.
HLSL: Add missing BuiltInLayer to HLSL backend.

KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross