qt-online-installer-windows-x64-4.8.1.exe --mirror http://mirrors.ustc.edu.cn/qtproject/
./qt-unified-linux-x64-online.run --mirror http://mirrors.ustc.edu.cn/qtproject/
open qt-online-installer-macos-x64-4.8.1.app --args --mirror http://mirrors.ustc.edu.cn/qtproject/