ref: c2a5d7e3f28e86aeef1e4e37e2b88e46af90b62c dir: /sys/src/ape/lib/ap/gen/strcat.c/
#include <string.h> char* strcat(char *s1, const char *s2) { strcpy(strchr(s1, 0), s2); return s1; }