ams: deduplicate static initialization logic

libraries/libstratosphere/source/erpt/srv/erpt_srv_keys.cpp

@@ -73,18 +73,7 @@ namespace ams::erpt::srv {
         }
 
         bool IsProductionMode() {
-            static constinit bool s_initialized  = false;
-            static constinit bool s_is_prod_mode = true;
-            static constinit os::SdkMutex s_mutex;
-
-            if (AMS_UNLIKELY(!s_initialized)) {
-                std::scoped_lock lk(s_mutex);
-
-                if (AMS_LIKELY(!s_initialized)) {
-                    s_is_prod_mode = IsProductionModeImpl();
-                    s_initialized = true;
-                }
-            }
+            AMS_FUNCTION_LOCAL_STATIC(bool, s_is_prod_mode, IsProductionModeImpl());
 
             return s_is_prod_mode;
         }