:: doesn't work on macro expansion

Index: mu/mu-cmd-server.cc
--- mu/mu-cmd-server.cc.orig
+++ mu/mu-cmd-server.cc
@@ -130,7 +130,7 @@ Mu::mu_cmd_server(const MuConfig* opts) try {
 		  opts->debug ? "yes" : "no",
 		  have_readline() ? "yes" : "no");
 
-	tty = ::isatty(::fileno(stdout));
+	tty = ::isatty(fileno(stdout));
 	const auto eval = std::string{opts->commands ? "(help :full t)"
 				      : opts->eval   ? opts->eval
 						     : ""};