Fix compilation errors with `feature = io_safety`. #1182

Job	Run time
Check tokio02 feature	26s
Build with no-std	13s
Check io_safety feature (ubuntu-latest)	40s
Check wasm targets (nightly)	27s
Check io_safety feature (windows-latest)	36s
Build and test (ubuntu-latest, nightly)	23s
Check wasm targets (beta)	24s
Build and test (ubuntu-latest, beta)	25s
Cross compile (i686-unknown-linux-gnu)	1m 11s
Check wasm targets (stable)	30s
Build and test (ubuntu-latest, stable)	25s
Cross compile (powerpc-unknown-linux-gnu)	1m 27s
Cross compile (powerpc64-unknown-linux-gnu)	1m 12s
Build and test (windows-latest, nightly)	1s
Checking fmt and docs	32s
Cross compile (arm-linux-androideabi)	1m 25s
Build and test (windows-latest, beta)	24s
Build and test (windows-latest, stable)	25s
Build and test (macOS-latest, nightly)	27s
Build and test (macOS-latest, beta)	23s
Build and test (macOS-latest, stable)	22s
	12m 18s

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