[clang][bytecode] Fix OptionScope initializer (llvm#155149)

Initialize the `OldToLValue` member with the actual old value of
`ToLValue`.

Pointed out by Shafik in
llvm#153601 (comment)

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -62,7 +62,7 @@ template <class Emitter> class OptionScope final {
   OptionScope(Compiler<Emitter> *Ctx, bool NewDiscardResult,
               bool NewInitializing, bool NewToLValue)
       : Ctx(Ctx), OldDiscardResult(Ctx->DiscardResult),
-        OldInitializing(Ctx->Initializing), OldToLValue(NewToLValue) {
+        OldInitializing(Ctx->Initializing), OldToLValue(Ctx->ToLValue) {
     Ctx->DiscardResult = NewDiscardResult;
     Ctx->Initializing = NewInitializing;
     Ctx->ToLValue = NewToLValue;