Add Void Linux to system update checking

functions

@@ -268,11 +268,13 @@ check_rc_update () {
 }
 
 check_sys_update () {
-    case $(lsb_release -a | awk -F ':\t' '/Distributor ID/{print $2}') in
+    case $(lsb_release -i | awk -F ':\t' '/Distributor ID/{print $2}') in
         Arch)
             nb_maj=$(checkupdates | wc -l);;
         Debian|Ubuntu)
             nb_maj=$(aptitude search '~U' | wc -l);;
+        VoidLinux)
+            nb_maj=$(xbps-install -Sun | wc -l);;
     esac
     if [ $nb_maj -gt 0 ]; then
         echo "update_sys $nb_maj" >> /dev/shm/prompt_msg