In `src/wren_value.h`, change three flexible array members (`char value[]`, `Upvalue* upvalues[]`, `Value fields[]`) to explicit zero-sized arrays (`char value[0]`, `Upvalue* upvalues[0]`, `Value fields[0]`) to resolve compiler warnings about non-standard zero-sized array usage in structs `ObjString`, `ObjClosure`, and `ObjInstance`.