学习笔记：安装flutter

中国区

 $ export PUB_HOSTED_URL=https://pub.flutter-io.cn
 $ export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn
 $ git clone -b dev https://github.com/flutter/flutter.git
 $ export PATH="$PWD/flutter/bin:$PATH"
 $ cd ./flutter
 $ flutter doctor

根据flutter doctor的输出结果，按照提示按照即可