Linux: Fix crash on invalid command-line arguments

use std::cout instead of wxMessageBox which does not work when wxWidgets has not been initialised yet

src/config/LaunchSettings.cpp

@@ -199,7 +199,11 @@ bool LaunchSettings::HandleCommandline(const std::vector<std::wstring>& args)
 		std::string errorMsg;
 		errorMsg.append("Error while trying to parse command line parameter:\n");
 		errorMsg.append(ex.what());
+#if BOOST_OS_WINDOWS
 		wxMessageBox(errorMsg, "Parameter error", wxICON_ERROR);
+#else
+		std::cout << errorMsg << std::endl;
+#endif
 		return false;
 	}