tests: added utils.cpp to avoid gcc warnings

tests/utils.cpp

@@ -0,0 +1,11 @@
+#include "includes.h"
+
+void prepare_logdir()
+{
+    spdlog::drop_all();
+#ifdef _WIN32
+    auto rv = system("del /F /Q logs\\*");
+#else
+    auto rv = system("rm -f logs/*");
+#endif
+}