message: Add debug facilities for single module building
diff: @@ -305,6 +305,8 @@ static CORE_MODULES: Lazy<HashSet<&'static str>> = Lazy::new(|| HashSet::from_it
  "viz",
  ].iter().copied()));
  +static DEBUG_MODULE: &str = "";
  +
  static MODULES: OnceCell<Vec<String>> = OnceCell::new();
  static OUT_DIR: Lazy<PathBuf> = Lazy::new(|| PathBuf::from(env::var_os("OUT_DIR").expect("Can't read OUT_DIR env var")));
  @@ -869,8 +871,9 @@ fn get_versioned_hub_dirs() -> (PathBuf, PathBuf) {
  }
  fn make_modules(opencv_dir_as_string: &str) -> Result<()> {
  - if MODULES.get().is_some() {
  - return Ok(());
  + if !DEBUG_MODULE.is_empty() {
  + MODULES.set(vec![DEBUG_MODULE.to_string()]).expect("Can't set debug MODULES cache");
  + return Ok(())
  }
  let ignore_modules: HashSet<&'static str> = HashSet::from_iter([
  "core_detect",
  