[autogen.sh:] Improve libtoolize invocation message.

Use the `$LIBTOOLIZE` variable inside the message to abstract over the two possible variants of the tool which
can be invoked.

Author: RandomDSdevel

autogen.sh

@@ -83,7 +83,7 @@ aclocal -I config || bail_out
 
 # --- Step 2:
 
-echo "Running libtoolize"
+echo "Running $LIBTOOLIZE"
 $LIBTOOLIZE -f -c || bail_out
 $LIBTOOLIZE --automake || bail_out