libstrat: enable -Wextra, -Werror

This caught an embarrassingly large number of bugs.

libraries/libstratosphere/source/htcs/client/htcs_virtual_socket_collection.cpp

@@ -602,7 +602,7 @@ namespace ams::htcs::client {
     }
 
     void VirtualSocketCollection::SetSize(s32 size) {
-        /* ... */
+        AMS_UNUSED(size);
     }
 
     s32 VirtualSocketCollection::Find(s32 id, s32 *error_code) {