Arm backend: Suppress cppcheck false positive in Cortex-M

[Sebastian-Larsson]

Document that the local weak fallback always returns 0, while some builds replace it with a driver implementation that can return an error.

Add a targeted cppcheck suppression for the weak-symbol error check without changing runtime behavior.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @robell

[pytorch-bot]

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❌ 3 New Failures, 8 Cancelled Jobs, 3 Unrelated Failures

As of commit 36807f2 with merge base a6ee309 ():

NEW FAILURES - The following jobs have failed:

• Build Presets / apple (llm) / build (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t bb7be665daef00bf991dd1a82cc0bfa9313c4b544687b8451ac57a8f86922805 /exec failed with exit code 1
• trunk / test-models-windows (vit, portable) / windows-job (gh)
  Process completed with exit code 1.

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• periodic / test-models-linux (buck2, mv3, portable, linux.2xlarge, 90) / linux-job (gh)
• periodic / test-models-linux (buck2, mv3, xnnpack-quantization-delegation, linux.2xlarge, 90) / linux-job (gh)
• periodic / test-models-linux (cmake, mv3, portable, linux.2xlarge, 90) / linux-job (gh)
• periodic / test-models-linux (cmake, mv3, xnnpack-quantization-delegation, linux.2xlarge, 90) / linux-job (gh)
• periodic / test-models-linux (cmake, vit, portable, linux.2xlarge, 90) / linux-job (gh)
• periodic / test-models-linux (cmake, vit, xnnpack-quantization-delegation, linux.2xlarge, 90) / linux-job (gh)
• Test CoreML Backend / test-coreml / test-backend-macos (coreml, operators) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-models-macos-coreml (resnet50) / macos-job (gh)
  ##[error]The operation was canceled.

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

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

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

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