mac系统下载WeCross Demo时出错

[wxl0357]

Describe the bug
使用macOS在根据WeCross的快速体验部分的文档进行操作时，在终端输入以下指令：
bash <(curl -sL https://gitee.com/WeBank/WeCross/raw/master/scripts/download_demo.sh)
然后就出现下述错误：/dev/fd/11: line 110: md5sum: command not found
[ERROR] Download package error
具体可看截图

To Reproduce
Steps to reproduce the behavior:

1. Download '...'
2. Run script '....'
3. Enter command '....'
4. Query information '....'

Expected behavior
希望能知道出现这种情况的原因

Screenshots

Desktop (please complete the following information):

• OS: [MACOS]
• Runtime: [e.g. libc, java]
• Version [e.g. openjdk 1.8]

Additional context
Add any other context about the problem here.

[kyonRay]

如错误所示，没有md5sum的命令，参考文档中环境依赖：https://wecross.readthedocs.io/zh_CN/latest/docs/tutorial/env.html#id4