ref: 82f0a1d2b47c3d1d7cf573a9f5008f95ddf3d092 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; }