Fail test if generated win_bindings.rs is different

tests/win_bindings.rs

@@ -11,5 +11,15 @@ fn gen_bindings() -> io::Result<()> {
     ];
 
     let bindings = windows_bindgen::standalone(&apis);
-    fs::write("src/offset/local/win_bindings.rs", format!("#![allow(unreachable_pub)]\n{bindings}"))
+
+    let path = "src/offset/local/win_bindings.rs";
+    let existing = fs::read_to_string(path)?;
+    // Skip the first two lines when comparing:
+    // - We add `#![allow(unreachable_pub)]` as a first line.
+    // - Rustfmt removes the empty line after the comment.
+    if !bindings.lines().skip(2).eq(existing.lines().skip(2)) {
+        fs::write(path, format!("#![allow(unreachable_pub)]\n{bindings}"))?;
+        panic!("generated file `{}` is changed.", path);
+    }
+    Ok(())
 }