fix version

Author: joaosaffran

clang/include/clang/Basic/LangOptions.h

@@ -549,8 +549,9 @@ class LangOptions : public LangOptionsBase {
   bool CheckNew = false;
 
   /// The HLSL root signature version for dxil.
+  /// This is kept at 1.1 to make it backwards compatible with DXC.
   llvm::dxbc::RootSignatureVersion HLSLRootSigVer =
-      llvm::dxbc::RootSignatureVersion::V1_2;
+      llvm::dxbc::RootSignatureVersion::V1_1;
 
   /// The HLSL root signature that will be used to overide the root signature
   /// used for the shader entry point.