Fix FFI-related bug

[squell]

No further comment.

[github-actions[bot]]

Number of dependencies and binary size impact report

Metric	main	PR #662	Delta
Direct dependencies	3	3	-
Total dependencies	4	4	-
Binary size	983.6 KiB	983.6 KiB	-
Text size	572.6 KiB	572.7 KiB	-

Dependencies diff

```diff └─ sudo-rs [v0.2.0-dev.20230703] ├─ glob [v0.3.1] ├─ libc [v0.2.147] └─ log [v0.4.19] ```

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: -27.61 :warning:

Comparison is base (a68aff7) 86.78% compared to head (7e62046) 59.17%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #662 +/- ## =========================================== - Coverage 86.78% 59.17% -27.61% =========================================== Files 61 66 +5 Lines 8595 8836 +241 =========================================== - Hits 7459 5229 -2230 - Misses 1136 3607 +2471 ``` | [Impacted Files](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/662?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/system/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/662?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3N5c3RlbS9tb2QucnM=) | `80.72% <100.00%> (-8.84%)` | :arrow_down: | ... and [50 files with indirect coverage changes](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/662/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety)

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