set emulate_precision_casts as true for cuda backend for better accuracy (#15005)

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the main branch.
ghstack PR number: #14983 by
@Gasoonjia
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ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/53/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/53/head
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Differential Revision:
[D84288174](https://our.internmc.facebook.com/intern/diff/D84288174/)
@diff-train-skip-merge

Co-authored-by: gasoonjia <[email protected]>
Co-authored-by: Gasoonjia <[email protected]>

Author: pytorchbot

backends/cuda/cuda_backend.py

@@ -129,6 +129,8 @@ def preprocess(
                 user_input_placeholders.append(node.meta["val"])
 
         options: dict[str, typing.Any] = {
+            # Better model precision
+            "emulate_precision_casts": True,
             # Embed CUDA kernel binaries directly into the compiled shared object
             "aot_inductor.embed_kernel_binary": True,
             # Do not link against the full PyTorch/libtorch library