[qfcc] Tweak ivar test to check old bug

It turns out that assigning nil to an ivar struct does not work (should,
of course).

tools/qfcc/test/ivar-struct-return.r

@@ -17,6 +17,7 @@ typedef struct Point Point;
 @implementation Object
 -(Point) origin
 {
+	origin = nil;
 	return origin;
 }
 @end