[clang][CIR] Fix build. NFC

- 'getStmtExprResult' is removed after d9c7c76. Use the original one to
  get the compound stmt's expr result.

clang/lib/CIR/CodeGen/CIRGenStmt.cpp

@@ -66,7 +66,7 @@ static mlir::LogicalResult emitStmtWithResult(CIRGenFunction &cgf,
 mlir::LogicalResult CIRGenFunction::emitCompoundStmtWithoutScope(
     const CompoundStmt &s, Address *lastValue, AggValueSlot slot) {
   mlir::LogicalResult result = mlir::success();
-  const Stmt *exprResult = s.getStmtExprResult();
+  const Stmt *exprResult = s.body_back();
   assert((!lastValue || (lastValue && exprResult)) &&
          "If lastValue is not null then the CompoundStmt must have a "
          "StmtExprResult");