Disable mean fallback op (#18815)

[mcremon-meta]

Summary:

POR models (and virtually anything else that I've seen) only use mean on floats. Removing the fallback by default saves 75.6kB in .text.

Differential Revision: D100258757

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/18815

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❌ 18 New Failures, 1 Cancelled Job, 1 Pending, 1 Unrelated Failure

As of commit ed75b5f with merge base 2c545f8 ():

NEW FAILURES - The following jobs have failed:

• pull / test-eval_llama-wikitext-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 515a2e35d804a5bca23a0c1c70adf15819ed57f812b16a5cd2e7bf5267326b60 /exec failed with exit code 1
• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.arm64.2xlarge, executorch-ubuntu-22.04-gc... / linux-job (gh)
  RuntimeError: Command docker exec -t 8ce6986d6f9d86728397889af4141680ea0a027f5dc16492a28c5642124e0982 /exec failed with exit code 1
• pull / test-llama-runner-linux (fp32, xnnpack+custom+quantize_kv, linux.arm64.2xlarge, executorch-ubuntu... / linux-job (gh)
  RuntimeError: Command docker exec -t ce57c486ec586530fc1480f06897fddce4618a0d5a5fe12548944f9cca42abf3 /exec failed with exit code 1
• pull / test-llama-runner-linux (fp32, xnnpack+quantize_kv, linux.arm64.2xlarge, executorch-ubuntu-22.04-... / linux-job (gh)
  RuntimeError: Command docker exec -t bd3f7f1faa829533dbe5d8c8658c4ad9580fa09976088cf78c66683ba35b6ada /exec failed with exit code 1
• pull / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh)
  RuntimeError: Command docker exec -t b4287aab680cd790cec5f1c63a6dffcdc24f9018569ecc5374346ebf655031a5 /exec failed with exit code 1
• pull / test-llama-runner-qnn-linux (fp32, qnn_8a8w, qnn) / linux-job (gh)
  RuntimeError: Command docker exec -t 5956361f336b46e66724e02a1b29f9419441d0639b9ac6fe7032c95725afdaa0 /exec failed with exit code 1
• pull / test-lora-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 6ad17a50d6cf7880f7cef12bcd33b2177dea0a8547b4fffe38b62a35c4af0101 /exec failed with exit code 1
• pull / test-lora-multimethod-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 915dbc37d2d7489b790821e87232aab5d7383571d3cc8dc6edc24a328ce9fa74 /exec failed with exit code 1
• pull / test-models-linux (ic4, portable, linux.4xlarge.memory) / linux-job (gh)
  RuntimeError: Command docker exec -t 3fb6fe933fceffe2d473d9e9afc3fd8d93580bc39678463f9fb6107b0db7035d /exec failed with exit code 1
• pull / test-models-linux (mobilebert, portable, linux.2xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t fddcbeb58f7d0f013e3946b5bfa22ab43b1ff17664a406f46feacd2c4a830ce6 /exec failed with exit code 1
• pull / test-models-linux (mobilebert, xnnpack-quantization-delegation, linux.2xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t 94a6fd61822223b94b07f8835c7d99d8629253a20cc464472f892ce0ece3e207 /exec failed with exit code 1
• pull / test-models-linux (phi_4_mini, portable, linux.4xlarge.memory) / linux-job (gh)
  RuntimeError: Command docker exec -t ff0d28251021df48834ac85323ee2086d1071e8aa867b2925d8380da2dd51691 /exec failed with exit code 1
• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t 3a06989095f7250242e3589059fcb66bfbe1a2980bd3127b212639f87293712b /exec failed with exit code 1
• pull / test-phi-3-mini-runner-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 9759be54347d028fa2a8a91351d47e1b6de5c8e6b3a52f055df96314d15a90da /exec failed with exit code 1
• pull / test-static-llama-qnn-linux (stories_110m) / linux-job (gh)
  test_llama_stories_110m
• pull / test-static-llama-qnn-linux (stories_260k_bc) / linux-job (gh)
  test_llama_stories_260k
• pull / test-voxtral-realtime-xnnpack-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 16188a79ec41a0fb5c0d0b5a7083c5f8fae5ea0cff154a76e3f0d542474e1f8a /exec failed with exit code 1
• pull / unittest-arm-backend-with-no-deps (test_pytest_models_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 049336e851ac5056e193c21ef109a59bee4fe34343d87db2217343ab1925f900 /exec failed with exit code 1

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / unittest-editable / windows / windows-job (gh)

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[meta-codesync]

@mcremon-meta has exported this pull request. If you are a Meta employee, you can view the originating Diff in D100258757.

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