tests/posix: Add tests for swab #1001

Job	Run time
Compile sysdeps (dripos)	2m 24s
Build mlibc (x86_64, mlibc, gcc)	2m 59s
Compile sysdeps (lemon)	2m 23s
Compile sysdeps (aero)	2m 23s
Build mlibc (x86_64, mlibc-static, gcc)	2m 59s
Compile sysdeps (ironclad)	2m 25s
Build mlibc (x86_64, mlibc-shared, gcc)	2m 58s
Build mlibc (x86_64, mlibc-ansi-only, gcc)	3m 1s
Compile sysdeps (lyre)	2m 19s
Build mlibc (x86_64, mlibc-headers-only, gcc)	2m 5s
Compile sysdeps (keyronex)	2m 20s
Build mlibc (riscv64, mlibc, gcc)	2m 59s
Compile sysdeps (managarm)	2m 27s
Build mlibc (riscv64, mlibc-static, gcc)	2m 58s
Compile sysdeps (vinix)	2m 19s
Build mlibc (riscv64, mlibc-shared, gcc)	2m 56s
Compile sysdeps (astral)	2m 24s
Build mlibc (riscv64, mlibc-ansi-only, gcc)	2m 54s
Build mlibc (riscv64, mlibc-headers-only, gcc)	2m 9s
Build mlibc (aarch64, mlibc, gcc)	3m 1s
Build mlibc (aarch64, mlibc-static, gcc)	3m 0s
Build mlibc (aarch64, mlibc-shared, gcc)	2m 59s
Build mlibc (aarch64, mlibc-ansi-only, gcc)	2m 59s
Build mlibc (aarch64, mlibc-headers-only, gcc)	2m 8s
Build mlibc (x86, mlibc, gcc)	3m 0s
Build mlibc (x86, mlibc-static, gcc)	2m 58s
Build mlibc (x86, mlibc-shared, gcc)	2m 57s
Build mlibc (x86, mlibc-ansi-only, gcc)	2m 57s
Build mlibc (x86, mlibc-headers-only, gcc)	2m 2s
Build mlibc (x86_64, mlibc, clang)	3m 0s
	1h 20m 23s

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