Don't try to remove an empty output_obj here.

This gets rid of the annoying:
rm: invalid argument: `'
I was seeing.
(I really shouldn't be hacking libtool)

ltmain.sh

@@ -863,12 +863,13 @@ EOF
       fi
 
       if test -z "$output_obj"; then
+	$run $rm "$lobj"
 	# Place PIC objects in $objdir
 	command="$command -o $lobj"
+      else
+	$run $rm "$lobj" "$output_obj"
       fi
 
-      $run $rm "$lobj" "$output_obj"
-
       $show "$command"
       if $run eval "$command"; then :
       else