Fix allocator mismatch with CompileWithDebug output string (#2137)

We declare CHeapPtr<wchar_t> DebugBlobName;, where CHeapPtr uses the CCRTAllocator by default, but initialize it with: Unicode::UTF8BufferToUTF16ComHeap(pDebugName, &DebugBlobName), which uses CComHeapPtr<wchar_t> p;

If we don't hit any exceptions, things are fine because we end up doing: *ppDebugBlobName = DebugBlobName.Detach(); , so the destructor will be a no-op.

tools/clang/tools/dxcompiler/dxcompilerobj.cpp

@@ -342,7 +342,7 @@ public:
     HRESULT hr = S_OK;
     CComPtr<IDxcBlobEncoding> utf8Source;
     CComPtr<AbstractMemoryStream> pOutputStream;
-    CHeapPtr<wchar_t> DebugBlobName;
+    CComHeapPtr<wchar_t> DebugBlobName;
 
     DxcEtw_DXCompilerCompile_Start();
     pSourceName = (pSourceName && *pSourceName) ? pSourceName : L"hlsl.hlsl"; // declared optional, so pick a default