fix build on BUILD_PWAL=OFF

Author: ban-nobuhiro

test/start/start_test.cpp

@@ -6,7 +6,9 @@
 #include "gtest/gtest.h"
 #include "glog/logging.h"
 
+#ifdef PWAL
 #include "limestone/api/datastore.h"
+#endif
 
 #include "shirakami/api_diagnostic.h"
 #include "shirakami/database_options.h"