Add missing files

tests/tests/neg/error_messages/extern_specs/auxiliary/dup_extern_spec_aux.rs

@@ -0,0 +1 @@
+pub fn test01() {}

tests/tests/neg/error_messages/extern_specs/dup_extern_spec.rs

@@ -0,0 +1,12 @@
+//@aux-build:dup_extern_spec_aux.rs
+
+extern crate dup_extern_spec_aux;
+
+use dup_extern_spec_aux::test01;
+use flux_rs::*;
+
+#[extern_spec]
+fn test01();
+
+#[extern_spec]
+fn test01(); //~ERROR multiple extern specs

tests/tests/neg/error_messages/extern_specs/extern_spec_for_local_def.rs

@@ -0,0 +1,6 @@
+use flux_rs::*;
+
+fn test01() {}
+
+#[extern_spec]
+fn test01(); //~ERROR cannot add extern specs to local definition

tests/tests/neg/extern_specs/auxiliary/extern_spec_trait00_aux.rs

@@ -0,0 +1,3 @@
+pub trait MyTrait {
+    fn method(&self) -> Self;
+}