Ignore maybe-uninitialised on MacOS with GCC >= 11

[andrjohns]

Closes #453

[saghul]

Does this silence the warning?

diff --git a/cutils.h b/cutils.h
index 26436d4..6d0c994 100644
--- a/cutils.h
+++ b/cutils.h
@@ -484,6 +484,8 @@ uint64_t js__hrtime_ns(void);
 
 static inline size_t js__malloc_usable_size(const void *ptr)
 {
+    if (!ptr)
+        return 0;
 #if defined(__APPLE__)
     return malloc_size(ptr);
 #elif defined(_WIN32)

[andrjohns]

Unfortunately not. If you want to experiment with other approaches you can also see the warning in action here: https://godbolt.org/z/jq15nWz5d