升級mac系統後，brew報錯,重裝homebrew

升級mac系統後，brew報錯
brew update
Error: Running Homebrew as root is extremely dangerous and no longer supported.
As Homebrew does not drop privileges on installation you would be giving all
build scripts full access to your system.

直接從新安裝一個新版本brew便可；
mkdir homebrew && curl -L https://github.com/Homebrew/brew/tarball/master | tar xz --strip 1 -C homebrew