Fix invocation of builtin shell to have proper argc and argv.
diff --git a/chroot.c b/chroot.c
index bae9cd7..c10df7a 100644
--- a/chroot.c
+++ b/chroot.c
@@ -54,7 +54,9 @@
 			prog = "/bin/sh";
 		execlp(prog, prog, NULL);
 #else
-		shell_main(argc, argv);
+		char shell[] = "/bin/sh";
+		char *shell_argv[2] = { shell, NULL };
+		shell_main(1, shell_argv);
 		return EXIT_SUCCESS;
 #endif
 	}