Descriptor: compile error with add --gn-args use_clang_coverage=true

issue:https://gitee.com/openharmony/build_lite/issues/I6AUU2?from=project-issueSigned-off-by: Nlwx1153805 <longshining2@huawei.com>

hb_internal/common/config.py

@@ -58,12 +58,7 @@ class Config(metaclass=Singleton):
                                                        None)
         self._subsystem_config_json = config_content.get(
             'subsystem_config_json', None)
-        subsystem_config_overlay_path = os.path.join(self._root_path,
-            'build/subsystem_config_overlay.json')
-        if os.path.isfile(subsystem_config_overlay_path):
-            self._subsystem_config_overlay_json = 'build/subsystem_config_overlay.json'
-        else:
-            self._subsystem_config_overlay_json = ''
+        self._subsystem_config_overlay_json = 'build/subsystem_config_overlay.json'
         self.fs_attr = set()
         self.platform = platform.system()