Check if dir already exists before creating.

May be necessary on some platforms for the current dir (".").

opm/autodiff/FlowMain.hpp

@@ -328,12 +328,14 @@ namespace Opm
                 output_dir_ =
                     param_.getDefault("output_dir", std::string("."));
                 boost::filesystem::path fpath(output_dir_);
+                if (!is_directory(fpath)) {
                     try {
                         create_directories(fpath);
                     }
                     catch (...) {
                         OPM_THROW(std::runtime_error, "Creating directories failed: " << fpath);
                     }
+                }
                 // Write simulation parameters.
                 param_.writeParam(output_dir_ + "/simulation.param");
             }