Fix compilation on macOS and FreeBSD with --no-default-features. (#966) #3691

Job	Run time
Check nightly-only targets (nightly)	24s
Check --no-default-features (nightly)	55s
Check selected Tier 3 platforms (nightly)	3m 58s
Rustfmt	13s
Check (stable)	6m 18s
Check (nightly)	6m 13s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 4s
Check (1.63)	9m 42s
Test use-libc (ubuntu)	44s
Test (ubuntu)	46s
Test use-libc (i686-linux)	59s
Test (ubuntu-20.04)	44s
Test use-libc (aarch64-linux)	1m 19s
Test (i686-linux)	1m 9s
Test use-libc (powerpc64le-linux)	1m 4s
Test (aarch64-linux)	1m 11s
Test use-libc (riscv64-linux)	1m 5s
Test (powerpc64le-linux)	1m 2s
Test use-libc (arm-linux)	1m 20s
Test (riscv64-linux)	1m 2s
Test (s390x-linux)	1m 3s
Test (arm-linux)	1m 6s
Test (ubuntu-stable)	48s
Test (i686-linux-stable)	1m 5s
Test (aarch64-linux-stable)	1m 15s
Test (riscv64-linux-stable)	1m 8s
Test (s390x-linux-stable)	1m 33s
Test (powerpc64le-linux-stable)	1m 5s
Test (arm-linux-stable)	1m 19s
Test (ubuntu-1.63)	1m 16s
Test (i686-linux-1.63)	1m 46s
Test (aarch64-linux-1.63)	2m 7s
Test (riscv64-linux-1.63)	1m 46s
Test (s390x-linux-1.63)	1m 45s
Test (powerpc64le-linux-1.63)	3m 19s
Test (arm-linux-1.63)	1m 41s
Test (macos-latest)	1m 40s
Test (macos-11)	1m 19s
Test (windows)	44s
Test (windows-2019)	49s
Test (musl)	51s
	1h 10m 37s

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