报错内容：rust src/openssl_shim.c:1:10: fatal error: 'openssl/hmac.h' file not found
failed to run custom build command for `openssl-sys-extras v0.7.4`
解决：
export OPENSSL_INCLUDE_DIR=/usr/local/Cellar/openssl/1.0.2s/include \
export OPENSSL_LIB_DIR=/usr/local/Cellar/openssl/1.0.2s/lib \
cargo clean
cargo build
参考：https://stackoverflow.com/questions/34612395/openssl-crate-fails-compilation-on-mac-os-x-10-11