tools/nolibc: implement wait() in terms of waitpid()

tools/nolibc: implement wait() in terms of waitpid()

Newer architectures like riscv 32-bit are missing sys_wait4().
Make use of the fact that wait(&status) is defined to be equivalent to
waitpid(-1, status, 0) to implement it on all architectures.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-15-3c043eeab06c@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>