编译SDWebImage Demo错误：libwebp/src/utils/random.c not found

从https://github.com/rs/SDWebImage处下载ZIP文件，编译会出现如下的错误

clang: error: no such file or directory: 'SDWebImage/Vendors/libwebp/src/utils/random.c'clang: error: no input files

参考这两处：

http://stackoverflow.com/questions/21074120/compiling-sdwebimage-demo-libwebp-src-utils-random-c-not-found

https://github.com/rs/SDWebImage/issues/756

使用 

git clone --recursive https://github.com/rs/SDWebImage.git

来下载代码可解决问题

SDWebImage代码如下：下载