Adds another lint example using extern "system"

test_crates/pub_function_changed_abi/new/src/lib.rs

@@ -11,3 +11,5 @@ pub extern "Rust" fn implicit_c_function_becomes_rust() -> () {}
 pub extern "Rust" fn rust_function_remains_rust() -> () {}
 
 pub extern "C" fn c_function_remains_c() -> () {}
+
+pub extern "C" fn system_function_becomes_c() -> () {}

test_crates/pub_function_changed_abi/old/src/lib.rs

@@ -11,3 +11,5 @@ pub extern fn implicit_c_function_becomes_rust() -> () {}
 pub extern "Rust" fn rust_function_remains_rust() -> () {}
 
 pub extern "C" fn c_function_remains_c() -> () {}
+
+pub extern "system" fn system_function_becomes_c() -> () {}

test_outputs/pub_function_changed_abi.output.ron

@@ -60,5 +60,17 @@
             "span_filename": String("src/lib.rs"),
             "visibility_limit": String("public"),
         },
+        {
+            "abi_name": String("system"),
+            "name": String("system_function_becomes_c"),
+            "new_abi_name": String("C"),
+            "path": List([
+                String("pub_function_changed_abi"),
+                String("system_function_becomes_c"),
+            ]),
+            "span_begin_line": Uint64(15),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
     ],
 }