Meson: Only trigger meson introspection files parsesing on file change

FileSystemWatcher was triggered before meson-info.json was written which most of the
time did just ignore last changes. When meson plugin is parsing the project, it discardes
all new parsing requests.

Change-Id: I20c8e95e5ed330628614a9fe1485394fd6b9fde8
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/mesonprojectmanager/project/mesonbuildsystem.cpp

@@ -196,7 +196,7 @@ void MesonBuildSystem::init()
                                .pathAppended(Constants::MESON_INFO_DIR)
                                .pathAppended(Constants::MESON_INFO)
                                .toString(),
-                           Utils::FileSystemWatcher::WatchAllChanges);
+                           Utils::FileSystemWatcher::WatchModifiedDate);
 }
 
 bool MesonBuildSystem::parseProject()