libstrat: enable -Wextra, -Werror

This caught an embarrassingly large number of bugs.

libraries/libstratosphere/source/erpt/srv/erpt_srv_allocator.hpp

@@ -44,6 +44,8 @@ namespace ams::erpt::srv {
     }
 
     inline void DeallocateWithSize(void *p, size_t size) {
+        AMS_UNUSED(size);
+
         return lmem::FreeToExpHeap(g_heap_handle, p);
     }