[clang] [llvm] [NFC][HLSL][DirectX] Let `HLSLRootSignature` reuse the `dxbc` defined enums (PR #145986)

[Finn Plummer via llvm-commits]

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@@ -274,11 +286,23 @@ TEST(HLSLRootSignatureTest, NoneRootFlagsDump) {
 }
 
 TEST(HLSLRootSignatureTest, AllRootFlagsDump) {
-  RootFlags Flags = RootFlags::ValidFlags;
+  using llvm::dxbc::RootFlags;
+  auto ValidRootFlags = RootFlags::AllowInputAssemblerInputLayout |
+                        RootFlags::DenyVertexShaderRootAccess |
+                        RootFlags::DenyHullShaderRootAccess |
+                        RootFlags::DenyDomainShaderRootAccess |
+                        RootFlags::DenyGeometryShaderRootAccess |
+                        RootFlags::DenyPixelShaderRootAccess |
+                        RootFlags::AllowStreamOutput |
+                        RootFlags::LocalRootSignature |
+                        RootFlags::DenyAmplificationShaderRootAccess |
+                        RootFlags::DenyMeshShaderRootAccess |
+                        RootFlags::CBVSRVUAVHeapDirectlyIndexed |
+                        RootFlags::SamplerHeapDirectlyIndexed;
 
   std::string Out;
   llvm::raw_string_ostream OS(Out);
-  OS << Flags;
+  OS << ValidFlags;
----------------
inbelic wrote:

```suggestion
  OS << ValidRootFlags;
```

https://github.com/llvm/llvm-project/pull/145986