selftests/clone3: test clone3 with exit signal in flags

Verify that calling clone3 with an exit signal (SIGCHLD) in flags will
fail.

Signed-off-by: Tobias Klauser <[e-mail]>
Reviewed-by: Christian Brauner <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/clone3/clone3.c

···
 	uid_t uid = getuid();
 
 	ksft_print_header();
-	ksft_set_plan(18);
+	ksft_set_plan(19);
 	test_clone3_supported();
 
 	/* Just a simple clone3() should return 0.*/
···
 
 	/* Do a clone3() in a new time namespace */
 	test_clone3(CLONE_NEWTIME, 0, 0, CLONE3_ARGS_NO_TEST);
+
+	/* Do a clone3() with exit signal (SIGCHLD) in flags */
+	test_clone3(SIGCHLD, 0, -EINVAL, CLONE3_ARGS_NO_TEST);
 
 	ksft_finished();
 }