进入homebrew目录
cd $(brew --prefix)/Homebrew/Library/Taps/homebrew/homebrew-core/Formula
查看git的提交记录
git log --follow icu4c.rb
切换到64.2的提交
git checkout -b icu4c-64.2 896d1018c7a4906f2c3fa1386aaf283497db60a2
brew重新安装icu4c
brew reinstall ./icu4c.rb