Add setdomainname function #4521

Job	Run time
Check --no-default-features (nightly)	55s
Check (stable)	5m 57s
Check selected Tier 3 platforms (nightly)	5m 6s
Check nightly-only targets (nightly)	22s
Check (nightly)	6m 15s
Check (1.63)	9m 38s
Rustfmt	5s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 18s
Test (ubuntu)	48s
Test rustix_use_experimental_asm (s390x-linux)	1m 7s
Test use-libc (ubuntu)	41s
Test (ubuntu-20.04)	44s
Test use-libc (i686-linux)	1m 23s
Test use-libc (aarch64-linux)	1m 22s
Test (i686-linux)	1m 16s
Test use-libc (powerpc64le-linux)	1m 16s
Test (aarch64-linux)	1m 10s
Test use-libc (riscv64-linux)	1m 10s
Test (powerpc64le-linux)	1m 16s
Test use-libc (s390x-linux)	1m 28s
Test use-libc (arm-linux)	1m 9s
Test (riscv64-linux)	1m 15s
Test (s390x-linux)	1m 19s
Test (arm-linux)	1m 16s
Test (ubuntu-stable)	42s
Test (i686-linux-stable)	1m 15s
Test (aarch64-linux-stable)	1m 12s
Test (riscv64-linux-stable)	1m 12s
Test (s390x-linux-stable)	1m 14s
Test (powerpc64le-linux-stable)	1m 19s
Test (arm-linux-stable)	1m 14s
Test (ubuntu-1.63)	1m 54s
Test (i686-linux-1.63)	2m 13s
Test (aarch64-linux-1.63)	2m 12s
Test (riscv64-linux-1.63)	2m 24s
Test (s390x-linux-1.63)	2m 27s
Test (powerpc64le-linux-1.63)	2m 24s
Test (arm-linux-1.63)	2m 22s
Test (macos-latest)	33s
Test (macos-13)	1m 20s
Test (windows)	53s
Test (windows-2019)	55s
Test (musl)	41s
	1h 16m 42s

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