mac-brew更新速慢，更改镜像源

1、替换brew.git
cd "$(brew --repo)"
git remote set-url origin https://mirrors.ustc.edu.cn/brew.git

2、替换homebrew-core.git
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git

3、替换homebrew-cash.git
cd "$(brew --repo)"/Library/Taps/homebrew/homebrew-cask
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-cask.git

4、更新brew
brew update