Fix apple platforms other than macOS

[dtolnay]

Fixes #242.

Tested:

• cargo check --target=aarch64-apple-darwin
• cargo check --target=aarch64-apple-ios
• cargo check --target=aarch64-apple-tvos
• cargo check --target=aarch64-apple-visionos
• cargo check --target=aarch64-apple-watchos

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.20%. Comparing base (7e4d3ac) to head (6674048).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #243      +/-   ##
==========================================
+ Coverage   85.47%   86.20%   +0.72%     
==========================================
  Files          14       16       +2     
  Lines        1818     2000     +182     
==========================================
+ Hits         1554     1724     +170     
- Misses        264      276      +12     

Flag	Coverage Δ
macos-latest	85.51% <ø> (?)
ubuntu-latest	85.78% <ø> (?)

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[ids1024]

Thanks!

Perhaps we could have some cargo check tests on CI. Though it looks there is a macOS CI test already. (Cirrus CI is shutting down, so the FreeBSD CI is going to need to be replaced or removed.)