Remember to return EXIT_FAILURE from main()

Doesn't matter in this case but gets rid of compiler warnings.

switch_root.c

@@ -134,4 +134,5 @@ main(int argc, char **argv)
 	/* execute init */
 	execv(argv[1], argv);
 	eprintf("can't execute '%s'\n", argv[1]);
+	return EXIT_FAILURE;
 }