MacOS 11 安装 cocoaPods

1. 更新ruby
   curl -sSL https://get.rvm.io | bash -s stable
   source ~/.rvm/scripts/rvm
   rvm -v
   rvm list known
   rvm install ruby-3.0.0

2. 安装cocoaPods
   gem sources --remove https://rubygems.org/
   gem sources --add https://gems.ruby-china.com/
   sudo gem install -n /usr/local/bin cocoapods

git clone https://mirrors.tuna.tsinghua.edu.cn/git/CocoaPods/Specs.git ~/.cocoapods/repos/master

3. 验证
   pod search AFNetworking