Fixed missing cfg.cpp

src/cfg.cpp

@@ -0,0 +1,8 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#ifndef SPDLOG_COMPILED_LIB
+#error Please define SPDLOG_COMPILED_LIB to compile this file.
+#endif
+
+#include "spdlog/cfg/helpers-inl.h"