Don't run twice on same directory on same moment

* We can't run optimize script twice on same instant

optimize.sh

@@ -103,6 +103,18 @@ else
     done
 fi
 
+##################################
+# Prevent multi execution on same directory
+##################################
+lock=$(echo -n "$IMG_PATH" | md5sum)
+
+if [ -f "/tmp/$lock" ]; then
+    echo "$IMG_PATH yet in progress"
+    exit 1
+else
+    touch "/tmp/$lock"
+fi
+
 ##################################
 # Welcome
 ##################################
@@ -220,3 +232,6 @@ fi
 echo ""
 echo -e "       ${CGREEN}Image optimization performed successfully !${CEND}"
 echo ""
+
+# Free ressource
+rm "/tmp/$lock"