Fix BLAS build flags in D3D12RaytracingOpacityMicromaps.cpp (#916)

* Fix BLAS build flags in D3D12RaytracingOpacityMicromaps.cpp

BLAS must be created with D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_ALLOW_DISABLE_OMMS to allow disabling OMMs at the instance level.

* Fix duplicate semi-colon.

Author: purplemunster

Samples/Desktop/D3D12Raytracing/src/D3D12RaytracingOpacityMicromaps/D3D12RaytracingOpacityMicromaps.cpp

@@ -591,7 +591,8 @@ void D3D12RaytracingOpacityMicromaps::BuildAccelerationStructures(bool updateUpl
         indexOffset += m_indicesPerGeom[i];
     }
 
-    D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAGS buildFlags = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_PREFER_FAST_TRACE;
+    D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAGS buildFlags =
+	D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_PREFER_FAST_TRACE | D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_ALLOW_DISABLE_OMMS;
 
     D3D12_RAYTRACING_OPACITY_MICROMAP_ARRAY_DESC ommArrayDesc = {};
     ommArrayDesc.InputBuffer = ommSet.arrayBuffer.defaultResource->GetGPUVirtualAddress();
@@ -1316,4 +1317,4 @@ void D3D12RaytracingOpacityMicromaps::OnSizeChanged(UINT width, UINT height, boo
 
     ReleaseWindowSizeDependentResources();
     CreateWindowSizeDependentResources();
-}
+}