MAC解决homebrew网络慢

tip:亲测有效

安装brew步骤（如果已经安装好，可跳过该步骤）：

1.任意位置打开终端，执行如下命令，下载brew安装的shell脚本
- curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh >> brew_install.sh
执行后生成一个brew_install.sh的shell脚本
2.修改brew_install.sh脚本
- vi brew_install.sh
全局查找BREW_REPO = "https://github.com/Homebrew/brew"参数
修改BREW_REPO的值为
BREW_REPO = "https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git"
- 3.增加可执行权限，执行该脚本进行安装
  - chmod 777 brew_install.sh
  - ./brew_install.sh
- 4.如果到该步卡住了：
```
==> Tapping homebrew/core
    Cloning into ‘/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core’…
```
  - 停止安装，进入如下文件夹：/usr/local/Homebrew/Library/
  - 删除Taps文件夹
  - 执行git clone git://mirrors.ustc.edu.cn/homebrew-core.git/ /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core --depth=1
  - 5.安装成功：
镜像换源
```
cd $(brew --repo)
```

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

接下来执行`brew update`会发现变快了很多