Fix new warnings on nightly #4301

Job	Run time
Rustfmt	4s
Check nightly-only targets (nightly)	22s
Check --no-default-features (nightly)	53s
Check (stable)	6m 1s
Check selected Tier 3 platforms (nightly)	4m 47s
Check (nightly)	6m 14s
Check (1.63)	9m 18s
Test rustix_use_experimental_asm (powerpc64le-linux)	55s
Test (ubuntu)	43s
Test use-libc (ubuntu)	35s
Test (ubuntu-20.04)	44s
Test use-libc (i686-linux)	57s
Test use-libc (aarch64-linux)	57s
Test (i686-linux)	1m 4s
Test use-libc (powerpc64le-linux)	54s
Test (aarch64-linux)	1m 11s
Test use-libc (riscv64-linux)	52s
Test (powerpc64le-linux)	1m 5s
Test use-libc (arm-linux)	1m 0s
Test (riscv64-linux)	1m 4s
Test (s390x-linux)	1m 6s
Test (arm-linux)	1m 4s
Test (ubuntu-stable)	36s
Test (i686-linux-stable)	59s
Test (aarch64-linux-stable)	1m 3s
Test (riscv64-linux-stable)	1m 5s
Test (s390x-linux-stable)	54s
Test (powerpc64le-linux-stable)	3m 34s
Test (arm-linux-stable)	1m 3s
Test (ubuntu-1.63)	1m 28s
Test (i686-linux-1.63)	1m 50s
Test (aarch64-linux-1.63)	1m 57s
Test (riscv64-linux-1.63)	1m 49s
Test (s390x-linux-1.63)	1m 45s
Test (powerpc64le-linux-1.63)	1m 41s
Test (arm-linux-1.63)	1m 56s
Test (macos-latest)	26s
Test (macos-12)	43s
Test (windows)	51s
Test (windows-2019)	53s
Test (musl)	42s
	1h 7m 5s

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