options/posix: Fix function prototype of pthread_exit #3289

Job	Run time
Build mlibc (x86_64, mlibc)	3m 57s
Build mlibc (x86_64, mlibc-static)	3m 14s
Compile sysdeps (dripos)	2m 21s
Build mlibc (x86_64, mlibc-shared)	3m 0s
Compile sysdeps (lemon)	2m 25s
Build mlibc (x86_64, mlibc-ansi-only)	2m 54s
Compile sysdeps (aero)	2m 19s
Build mlibc (x86_64, mlibc-headers-only)	1m 58s
Compile sysdeps (ironclad)	2m 20s
Build mlibc (riscv64, mlibc)	4m 2s
Compile sysdeps (lyre)	2m 21s
Build mlibc (riscv64, mlibc-static)	4m 44s
Compile sysdeps (keyronex)	2m 25s
Build mlibc (riscv64, mlibc-shared)	3m 24s
Build mlibc (riscv64, mlibc-ansi-only)	2m 49s
Build mlibc (riscv64, mlibc-headers-only)	2m 16s
Build mlibc (aarch64, mlibc)	3m 59s
Build mlibc (aarch64, mlibc-static)	3m 16s
Build mlibc (aarch64, mlibc-shared)	3m 14s
Build mlibc (aarch64, mlibc-ansi-only)	3m 9s
Build mlibc (aarch64, mlibc-headers-only)	1m 54s
Build mlibc (x86, mlibc)	4m 9s
Build mlibc (x86, mlibc-static)	3m 18s
Build mlibc (x86, mlibc-shared)	3m 29s
Build mlibc (x86, mlibc-ansi-only)	3m 2s
Build mlibc (x86, mlibc-headers-only)	2m 57s
	1h 18m 56s

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