rustix: on Linux, support a build without linux-raw-sys #5317

Job	Run time
Check --no-default-features (nightly)	56s
Rustfmt	8s
Check (1.63)	10m 52s
Check (stable)	6m 39s
Check (nightly)	6m 34s
Check selected Tier 3 platforms (nightly)	5m 48s
Check nightly-only targets (nightly)	23s
Test rustix_use_experimental_asm (s390x-linux)	2m 21s
Test rustix_use_experimental_asm (powerpc-linux)	2m 2s
Test use-libc (i686-linux)	33s
Test rustix_use_experimental_asm (powerpc64le-linux)	2m 31s
Test use-libc (ubuntu)	29s
Test use-libc (aarch64-linux)	43s
Test use-libc (riscv64-linux)	44s
Test use-libc (arm-linux)	43s
Test use-libc (s390x-linux)	44s
Test use-libc (powerpc64le-linux)	33s
Test use-libc (powerpc-linux)	43s
Test (ubuntu-22.04)	46s
Test (ubuntu)	47s
Test (aarch64-linux)	1m 1s
Test (riscv64-linux)	1m 1s
Test (powerpc64le-linux)	1m 1s
Test (s390x-linux)	1m 2s
Test (i686-linux)	1m 1s
Test (arm-linux)	1m 0s
Test (ubuntu-stable)	47s
Test (powerpc-linux)	1m 0s
Test (riscv64-linux-stable)	1m 0s
Test (i686-linux-1.63)	1m 1s
Test (ubuntu-1.63)	1m 0s
Test (arm-linux-stable)	1m 2s
Test (powerpc64le-linux-stable)	46s
Test (riscv64-linux-1.63)	1m 2s
Test (s390x-linux-stable)	1m 1s
Test (aarch64-linux-1.63)	1m 1s
Test (i686-linux-stable)	1m 2s
Test (powerpc-linux-stable)	54s
Test (s390x-linux-1.63)	1m 2s
Test (powerpc64le-linux)	1m 0s
Test (windows)	49s
Test (macos-latest)	45s
Test (arm-linux-1.63)	1m 2s
Test (windows-2019)	50s
Test (musl)	44s
Test (powerpc64le-linux-1.63)	1m 2s
Test (aarch64-linux-stable)	1m 1s
Test (powerpc-linux-1.63, ubuntu-latest, 1.63, powerpc-unknown-linux-gnu, gcc-powerpc-linux-gnu, ...	1m 2s
Test (macos-13)	37s
	1h 12m 35s

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