aux/listen1: allow alternative namespace when running as user none with -n option

sys/man/8/listen

@@ -20,6 +20,8 @@ listen, listen1, tcp7, tcp9, tcp19, tcp21, tcp22, tcp23, tcp25, tcp53, tcp110, t
 ]
 .RB [ -p
 .IR maxprocs ]
+.RB [ -n
+.IR namespace ]
 .I addr
 .I cmd
 [

sys/src/cmd/aux/listen1.c

@@ -5,6 +5,7 @@
 int maxprocs;
 int verbose;
 int trusted;
+char *nsfile;
 
 void
 usage(void)
@@ -22,7 +23,7 @@ becomenone(void)
 	if(fd < 0 || write(fd, "none", strlen("none")) < 0)
 		sysfatal("can't become none: %r");
 	close(fd);
-	if(newns("none", nil) < 0)
+	if(newns("none", nsfile) < 0)
 		sysfatal("can't build namespace: %r");
 }
 
@@ -69,6 +70,9 @@ main(int argc, char **argv)
 	case 'p':
 		maxprocs = atoi(EARGF(usage()));
 		break;
+	case 'n':
+		nsfile = EARGF(usage());
+		break;
 	}ARGEND
 
 	if(argc < 2)