[clang][Interp][NFC] const qualify a local variable

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -75,7 +75,7 @@ template <class Emitter> class OptionScope final {
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
-  auto *SubExpr = CE->getSubExpr();
+  const Expr *SubExpr = CE->getSubExpr();
   switch (CE->getCastKind()) {
 
   case CK_LValueToRValue: {