Add usage info to zip-tool utility

MD-19678 #time 5m

src/zip-tool.cpp

@@ -39,6 +39,9 @@ int main(int argc, char** argv)
 {
     if (argc < 3)
     {
+		std::cerr << "Usage: " << argv[0] << " <archive name> <input dir>" << std::endl << std::endl
+		          << "Recursively scan <input dir> and add all files found to the ZIP archive <archive name>"
+		          << std::endl;
         return 1;
     }