Avoid -Wstrict-prototypes diagnostics

Index: rts/sm/MarkWeak.c
--- rts/sm/MarkWeak.c.orig
+++ rts/sm/MarkWeak.c
@@ -453,7 +453,7 @@ static void checkWeakPtrSanity(StgWeak *hd, StgWeak *t
  * Traverse the capabilities' local new-weak-pointer lists at the beginning of
  * GC and move them to the nursery's weak_ptr_list.
  */
-void collectFreshWeakPtrs()
+void collectFreshWeakPtrs(void)
 {
     uint32_t i;
     // move recently allocated weak_ptr_list to the old list as well
