Buddy range: assert that MAX > MIN

Now that the case leading to several 0-sized arrays in Buddy ranges, that then
cause gcc's -Warray-bounds to trip, has been removed, add a static assert so
that we can catch this with better error messages next time.

src/snmalloc/backend_helpers/buddy.h

@@ -15,6 +15,8 @@ namespace snmalloc
   template<typename Rep, size_t MIN_SIZE_BITS, size_t MAX_SIZE_BITS>
   class Buddy
   {
+    static_assert(MAX_SIZE_BITS > MIN_SIZE_BITS);
+
     struct Entry
     {
       typename Rep::Contents cache[3];