warning MSB8004: Output Directory does not end with a trailing slash. This build instance will add the slash as it is required to allow proper evaluation of the Output Directory.
本着不放过任何一个warning的原则，查找原因。
trailing slash 反斜杠; 拖尾斜杠; 尾斜杠;
原因是因为输出目录没有以斜杠结尾，如下图
加上上图中的最后一个斜杠就可以啦