Fall back to `TCGETS` if `TCGETS2` fails #4209

Job	Run time
Check --no-default-features (nightly)	56s
Check selected Tier 3 platforms (nightly)	4m 30s
Check nightly-only targets (nightly)	22s
Check (stable)	6m 1s
Rustfmt	5s
Check (nightly)	6m 23s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 6s
Check (1.63)	11m 20s
Test (ubuntu)	42s
Test (ubuntu-20.04)	43s
Test use-libc (ubuntu)	36s
Test (i686-linux)	1m 5s
Test use-libc (i686-linux)	55s
Test (aarch64-linux)	1m 9s
Test use-libc (aarch64-linux)	1m 3s
Test (powerpc64le-linux)	1m 13s
Test use-libc (powerpc64le-linux)	1m 0s
Test (riscv64-linux)	1m 10s
Test use-libc (riscv64-linux)	1m 14s
Test (s390x-linux)	1m 6s
Test use-libc (arm-linux)	1m 10s
Test (arm-linux)	1m 5s
Test (ubuntu-stable)	35s
Test (i686-linux-stable)	1m 5s
Test (aarch64-linux-stable)	1m 5s
Test (riscv64-linux-stable)	1m 6s
Test (s390x-linux-stable)	1m 10s
Test (powerpc64le-linux-stable)	59s
Test (arm-linux-stable)	1m 7s
Test (ubuntu-1.63)	3m 32s
Test (i686-linux-1.63)	3m 47s
Test (aarch64-linux-1.63)	3m 53s
Test (riscv64-linux-1.63)	4m 4s
Test (s390x-linux-1.63)	3m 50s
Test (powerpc64le-linux-1.63)	3m 51s
Test (arm-linux-1.63)	3m 56s
Test (macos-latest)	18m 42s
Test (macos-12)	18m 56s
Test (windows)	57s
Test (windows-2019)	55s
Test (musl)	41s
	1h 59m 5s

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