review: explicitly use hash_code

Co-authored-by: Aaron Ballman <[email protected]>

Author: inbelic

clang/lib/Sema/SemaHLSL.cpp

@@ -973,7 +973,7 @@ void SemaHLSL::emitLogicalOperatorFixIt(Expr *LHS, Expr *RHS,
 
 std::pair<IdentifierInfo *, bool>
 SemaHLSL::ActOnStartRootSignatureDecl(StringRef Signature) {
-  auto Hash = llvm::hash_value(Signature);
+  llvm::hash_code Hash = llvm::hash_value(Signature);
   std::string IdStr = "__hlsl_rootsig_decl_" + std::to_string(Hash);
   IdentifierInfo *DeclIdent = &(getASTContext().Idents.get(IdStr));