metal : fix build(#17799)

* metal : fix build

* tests : fix context destruction

examples/save-load-state/save-load-state.cpp

@@ -241,6 +241,12 @@ int main(int argc, char ** argv) {
 
     llama_batch_free(batch);
 
+    // this one is managed by common_init_result
+    //llama_free(ctx);
+
+    llama_free(ctx2);
+    llama_free(ctx3);
+
     if (result0 != result2) {
         fprintf(stderr, "\n%s : error : the seq restore generation is different\n", __func__);
         return 1;