Fix miscellaneous clippy lints. #3476

Job	Run time
Rustfmt	11s
Check nightly-only targets (nightly)	37s
Check (stable)	3m 52s
Check --no-default-features (nightly)	44s
Check (nightly)	3m 39s
Check selected Tier 3 platforms (nightly)	8m 37s
Check (1.63)	3m 54s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 51s
Test (ubuntu)	1m 17s
Test use-libc (ubuntu)	1m 1s
Test (ubuntu-20.04)	1m 15s
Test use-libc (i686-linux)	1m 45s
Test (i686-linux)	1m 38s
Test use-libc (aarch64-linux)	2m 18s
Test (aarch64-linux)	1m 45s
Test use-libc (powerpc64le-linux)	1m 35s
Test (powerpc64le-linux)	1m 56s
Test use-libc (riscv64-linux)	1m 30s
Test (riscv64-linux)	1m 45s
Test use-libc (arm-linux)	1m 35s
Test (s390x-linux)	1m 34s
Test (arm-linux)	1m 35s
Test (ubuntu-stable)	1m 3s
Test (i686-linux-stable)	2m 3s
Test (aarch64-linux-stable)	1m 34s
Test (riscv64-linux-stable)	1m 39s
Test (s390x-linux-stable)	2m 8s
Test (powerpc64le-linux-stable)	1m 36s
Test (arm-linux-stable)	2m 38s
Test (ubuntu-1.63)	5m 30s
Test (i686-linux-1.63)	6m 48s
Test (aarch64-linux-1.63)	6m 0s
Test (riscv64-linux-1.63)	7m 7s
Test (s390x-linux-1.63)	6m 55s
Test (powerpc64le-linux-1.63)	7m 35s
Test (arm-linux-1.63)	7m 54s
Test (macos-latest)	19m 12s
Test (macos-11)	1m 25s
Test (windows)	1m 20s
Test (windows-2019)	1m 12s
	2h 9m 33s

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