官方说明
    https://github.com/aliyun/aliyun-oss-cpp-sdk/blob/master/README_zh.md

    git 命令获取SDK源码

    1. git clone https://github.com/aliyun/aliyun-oss-cpp-sdk.git

    cmake构建Xcode工程

    1. cmake -DOPENSSL_ROOT_DIR=/usr/local/Cellar/openssl/1.0.2s\
    2. -DOPENSSL_LIBRARIES=/usr/local/Cellar/openssl/1.0.2s/lib\
    3. -DOPENSSL_INCLUDE_DIRS=/usr/local/Cellar/openssl/1.0.2s/include ..