* src/ltltest/stutter.test: Run time only if present.

src/ltltest/stutter.test

 #! /bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2013, 2014 Laboratoire de Recherche et Développement
-# de l'Epita (LRDE).
+# Copyright (C) 2013, 2014, 2015 Laboratoire de Recherche et
+# Développement de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
 #
@@ -27,6 +27,12 @@ set -e
 randltl=../../bin/randltl
 ltlfilt=../../bin/ltlfilt
 
+# Use time only if it is available
+time=
+if (time ls) >/dev/null 2>&1; then
+    time=time
+fi
+
 FILE=formulae
 rm -f $FILE
 for i in 10 12 14 16 18 20; do
@@ -38,7 +44,7 @@ done
 for i in 1 2 3 4 5 6 7 8; do
     SPOT_STUTTER_CHECK=$i
     export SPOT_STUTTER_CHECK
-    time $ltlfilt --stutter-invariant -F $FILE > res.$i
+    $time $ltlfilt --stutter-invariant -F $FILE > res.$i
 done
 
 # All results should be equal