Add compile-fail test for the with attribute

test_suite/tests/compile-fail/duplicate-attribute/with-and-serialize-with.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+struct S {
+    #[serde(with = "w", serialize_with = "s")] //~^^ HELP: duplicate serde attribute `serialize_with`
+    x: (),
+}
+
+fn main() {}