Fix compilation on platforms without `SO_RCVBUFFORCE`. #4349

Job	Run time
Check nightly-only targets (nightly)	24s
Check --no-default-features (nightly)	56s
Check selected Tier 3 platforms (nightly)	5m 5s
Check (stable)	6m 14s
Rustfmt	10s
Check (nightly)	6m 15s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 7s
Check (1.63)	9m 37s
Test rustix_use_experimental_asm (s390x-linux)	1m 22s
Test use-libc (ubuntu)	44s
Test use-libc (i686-linux)	1m 11s
Test (ubuntu)	44s
Test use-libc (aarch64-linux)	1m 7s
Test (ubuntu-20.04)	48s
Test use-libc (powerpc64le-linux)	1m 27s
Test (i686-linux)	1m 5s
Test use-libc (riscv64-linux)	2m 28s
Test use-libc (s390x-linux)	1m 0s
Test (aarch64-linux)	1m 7s
Test use-libc (arm-linux)	1m 2s
Test (powerpc64le-linux)	1m 13s
Test (riscv64-linux)	2m 17s
Test (s390x-linux)	1m 5s
Test (arm-linux)	6m 26s
Test (ubuntu-stable)	1m 6s
Test (i686-linux-stable)	57s
Test (aarch64-linux-stable)	1m 17s
Test (riscv64-linux-stable)	2m 3s
Test (s390x-linux-stable)	1m 9s
Test (powerpc64le-linux-stable)	53s
Test (arm-linux-stable)	9m 9s
Test (ubuntu-1.63)	1m 50s
Test (i686-linux-1.63)	2m 9s
Test (aarch64-linux-1.63)	2m 44s
Test (riscv64-linux-1.63)	3m 18s
Test (s390x-linux-1.63)	2m 20s
Test (powerpc64le-linux-1.63)	2m 10s
Test (arm-linux-1.63)	7m 0s
Test (macos-latest)	29s
Test (macos-12)	42s
Test (windows)	49s
Test (windows-2019)	52s
Test (musl)	39s
	1h 36m 30s

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