message: Avoid patching the file `msdfgen_wasm.js` more than once.
  Adds a fix for a build issue where the `msdfgen_wasm.js` file gets patched multiple times, which breaks the build.
  [ci no changelog needed]
diff: @@ -43,9 +43,12 @@ mod msdfgen_wasm {
  let mut open_options = fs::OpenOptions::new();
  open_options.append(true);
  let mut file = open_options.open(path).unwrap();
  + let file_content = fs::read_to_string(path).unwrap();
  + if !file_content.ends_with(PATCH_LINE) {
  file.write_all(PATCH_LINE.as_bytes()).unwrap();
  }
  }
  +}
  fn main() {
  println!("cargo:rerun-if-changed=build.rs");
  