AUTOGRAD is not working on IOS
Labels: module: autograd, triaged, oncall: mobile, module: ios

### 🐛 Describe the bug

``Hello! 
I've built latest pytorch from sources with `BUILD_MOBILE_AUTOGRAD : ON` on ios. However, when I'm trying to reproduce the easiest autograd example, I get an error.
```c++
{
            torch::AutoGradMode enable_grad(true);
            
            auto x = torch::ones({2, 2}, torch::requires_grad());
            auto y = x + 2;
            y = y.sum();
            y.backward();
 }
 
```
ERROR_LOG: `element 0 of tensors does not require grad and does not have a grad_fn`

My initial task is to collect the gradients from forward pass in order to preprocess input(to perform forward pass again, and get more robust softmax scores).

Seems like autograd is not working.

### Versions

BUILD FLAGS
--   TORCH_VERSION         : 1.13.0
--   CAFFE2_VERSION        : 1.13.0
--   BUILD_CAFFE2          : OFF
--   BUILD_CAFFE2_OPS      : OFF
--   BUILD_STATIC_RUNTIME_BENCHMARK: OFF
--   BUILD_TENSOREXPR_BENCHMARK: OFF
--   BUILD_NVFUSER_BENCHMARK: OFF
--   BUILD_BINARY          : OFF
--   BUILD_CUSTOM_PROTOBUF : OFF
--     Protobuf compiler   : 
--     Protobuf includes   : 
--     Protobuf libraries  : 
--   BUILD_DOCS            : OFF
--   BUILD_PYTHON          : OFF
--   BUILD_SHARED_LIBS     : OFF
--   CAFFE2_USE_MSVC_STATIC_RUNTIME     : ON
--   BUILD_TEST            : OFF
--   BUILD_JNI             : OFF
--   BUILD_MOBILE_AUTOGRAD : ON
--   BUILD_LITE_INTERPRETER: ON
--   CROSS_COMPILING_MACOSX : 
--   INTERN_BUILD_MOBILE   : ON
--   TRACING_BASED         : OFF
--   USE_BLAS              : OFF
--   USE_LAPACK            : 0
--   USE_ASAN              : OFF
--   USE_CPP_CODE_COVERAGE : OFF
--   USE_CUDA              : OFF
--   USE_ROCM              : OFF
--   USE_EIGEN_FOR_BLAS    : ON
--   USE_FBGEMM            : OFF
--     USE_FAKELOWP          : OFF
--   USE_KINETO            : OFF
--   USE_FFMPEG            : OFF
--   USE_GFLAGS            : OFF
--   USE_GLOG              : OFF
--   USE_LEVELDB           : OFF
--   USE_LITE_PROTO        : OFF
--   USE_LMDB              : OFF
--   USE_METAL             : ON
--   USE_PYTORCH_METAL     : OFF
--   USE_PYTORCH_METAL_EXPORT     : OFF
--   USE_MPS               : OFF
--   USE_FFTW              : OFF
--   USE_MKL               : 
--   USE_MKLDNN            : OFF
--   USE_UCC               : OFF
--   USE_ITT               : OFF
--   USE_NCCL              : OFF
--   USE_NNPACK            : OFF
--   USE_NUMPY             : OFF
--   USE_OBSERVERS         : OFF
--   USE_OPENCL            : OFF
--   USE_OPENCV            : OFF
--   USE_OPENMP            : OFF
--   USE_TBB               : OFF
--   USE_VULKAN            : OFF
--   USE_PROF              : OFF
--   USE_QNNPACK           : OFF
--   USE_PYTORCH_QNNPACK   : ON
--   USE_XNNPACK           : ON
--   USE_REDIS             : OFF
--   USE_ROCKSDB           : OFF
--   USE_ZMQ               : OFF
--   USE_DISTRIBUTED       : OFF
--   USE_DEPLOY           : OFF
--   Public Dependencies  : caffe2::Threads
--   Private Dependencies : pthreadpool;cpuinfo;pytorch_qnnpack;XNNPACK;fp16;fmt::fmt-header-only
--   USE_COREML_DELEGATE     : OFF
--   BUILD_LAZY_TS_BACKEND   : OFF

cc @ezyang @albanD @zou3519 @gqchen @pearu @nikitaved @soulitzer @Lezcano @Varal7