Add function to check whether a board has an analogue jack

raspi-config

@@ -89,6 +89,14 @@ is_pulseaudio() {
   return $?
 }
 
+has_analog() {
+  if [ $(get_leds) -eq -1 ] ; then
+    return 0
+  else
+    return 1
+  fi
+}
+
 is_installed() {
     if [ "$(dpkg -l "$1" 2> /dev/null | tail -n 1 | cut -d ' ' -f 1)" != "ii" ]; then
       return 1