libc: fix strcpy()

Implemented strcat() accidentally.

libc/string/strcpy.cc

@@ -3,9 +3,6 @@
 char* strcpy(char* dest, const char* src)
 {
     char* p = dest;
-    while (*p) {
-        ++p;
-    }
     while (*src) {
         *p++ = *src++;
     }