Don't return but _exit after failed exec*() and fork()

Quoting POSIX[0]:
"Care should be taken, also, to call _exit() rather than exit() if exec cannot be used, since
exit() flushes and closes standard I/O channels, thereby damaging the parent process' standard
I/O data structures. (Even with fork(), it is wrong to call exit(), since buffered data would
then be flushed twice.)"

[0]: http://pubs.opengroup.org/onlinepubs/009695399/functions/vfork.html

chroot.c

@@ -36,15 +36,14 @@ main(int argc, char *argv[])
 
 	if (argc == 1) {
 		cmd = *shell;
-		execvp(*shell, shell);
+		execvp(cmd, shell);
 	} else {
 		cmd = argv[1];
-		execvp(argv[1], argv + 1);
+		execvp(cmd, argv + 1);
 	}
 
 	savederrno = errno;
 	weprintf("execvp %s:", cmd);
-	_exit(126 + (savederrno == ENOENT));
 
-	return 0; /* not reached */
+	_exit(126 + (savederrno == ENOENT));
 }