add log 4 annoy if index has been built when BuildAll interface invoked (#2071)

* add log 4 annoy if index has been built when BuildAll interface invoked
Signed-off-by: Ngrace <yan.gu@zilliz.com>

* fix lint error
Signed-off-by: Ngrace <yan.gu@zilliz.com>

core/src/index/knowhere/knowhere/index/vector_index/IndexAnnoy.cpp

@@ -85,6 +85,7 @@ void
 IndexAnnoy::BuildAll(const DatasetPtr& dataset_ptr, const Config& config) {
     if (index_) {
         // it is builded all
+        KNOWHERE_LOG_DEBUG << "IndexAnnoy::BuildAll: index_ has been built!";
         return;
     }