Fix `--config-location -`

yt_dlp/utils.py

@@ -5554,6 +5554,9 @@ class Config:
         self.parsed_args = self.own_args
         for location in opts.config_locations or []:
             if location == '-':
+                if location in self._loaded_paths:
+                    continue
+                self._loaded_paths.add(location)
                 self.append_config(shlex.split(read_stdin('options'), comments=True), label='stdin')
                 continue
             location = os.path.join(directory, expand_path(location))