Compile with -Wint-in-bool-context flag

[mergennachin]

🚀 The feature, motivation and pitch

Follow up to #8016

For gcc9, it is failing with int-in-bool-context errors (https://github.com/pytorch/executorch/actions/runs/13123890485/job/36616081625?pr=8016)

For now, I disabled that but we should make sure to clean those errors

Specifically for prod_op.cpp it is multiplying a boolean vector.

Alternatives

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Additional context

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RFC (Optional)

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cc @JacobSzwejbka @dbort