native/MASM divergence for `i64::checked_mul`

Reproduction requires #1140

```sh
cargo nextest run -p midenc-integration-tests \
--run-ignored all \
-E 'test(/checked_mul_i64_edge_case/)'
```

```
thread 'end_to_end::arithmetic::checked_mul_i64_edge_cases' (188951) panicked at tests/integration/src/end_to_end/arithmetic.rs:1082:13:
Found minimal(shrinked) failing case: (-4611686018427387904, 2)
Failure: Reason("assertion failed: `(left == right)` \n left: `[0, 0, 0, 0, 0, 0, 0, 128, 1]`, \n right: `[0, 0, 0, 0, 0, 0, 0, 128, 0]`: VM output mismatch at tests/integration/src/end_to_end/arithmetic.rs:1075")
```

The failing test is in tests/integration/src/end_to_end/arithmetic.rs, line 1082. Run the provided cargo nextest command to reproduce the divergence between native and MASM for i64::checked_mul with inputs (-4611686018427387904, 2). Examine the compiler's code generation for checked multiplication, focusing on overflow handling for 64-bit integers.

Rédigé par le modèle d'indexation à partir du texte de l'issue.