ref: 8adc5a0fce7e50f8bf8e69e51274092a1a581cd6
dir: /sys/src/ape/lib/ap/plan9/umask.c/
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
/*
 * No such concept in plan9, but supposed to be always successful
 */
mode_t
umask(mode_t)
{
	return 0;
}