Fix `sendmsg_unix`'s address encoding. (#885) #3458

Job	Run time
Check (stable)	3m 37s
Check (nightly)	4m 35s
Check (1.48)	11m 3s
Check selected Tier 3 platforms (nightly)	3m 28s
Check nightly-only targets (nightly)	34s
Check --no-default-features (nightly)	1m 1s
Rustfmt	5s
Test rustix_use_experimental_asm (powerpc64le-linux)	3m 24s
Test (ubuntu)	59s
Test use-libc (ubuntu)	45s
Test (ubuntu-20.04)	52s
Test use-libc (i686-linux)	1m 3s
Test (i686-linux)	1m 25s
Test use-libc (aarch64-linux)	3m 40s
Test (aarch64-linux)	4m 26s
Test use-libc (powerpc64le-linux)	3m 23s
Test (powerpc64le-linux)	2m 49s
Test (riscv64-linux)	3m 57s
Test use-libc (riscv64-linux)	3m 20s
Test (s390x-linux)	3m 20s
Test use-libc (arm-linux)	2m 48s
Test (arm-linux)	3m 15s
Test (ubuntu-stable)	44s
Test (ubuntu-1.48)	5m 51s
Test (i686-linux-stable)	1m 22s
Test (aarch64-linux-stable)	4m 17s
Test (riscv64-linux-stable)	3m 22s
Test (s390x-linux-stable)	2m 46s
Test (powerpc64le-linux-stable)	3m 20s
Test (arm-linux-stable)	2m 51s
Test (ubuntu-1.48)	5m 42s
Test (i686-linux-1.48)	5m 38s
Test (aarch64-linux-1.48)	7m 57s
Test (riscv64-linux-1.48)	9m 26s
Test (s390x-linux-1.48)	8m 35s
Test (powerpc64le-linux-1.48)	6m 57s
Test (arm-linux-1.48)	7m 31s
Test (macos-latest)	1m 43s
Test (macos-11)	1m 3s
Test (windows)	1m 14s
Test (windows-2019)	1m 18s
	2h 25m 26s

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