QT安装目录下打开MaintenanerceTool.exe
手动添加储存库，要定位一个储存有QT在线安装镜像的网址：
https://download.qt.io/online/qtsdkrepository/windows_x86/root/qt/
http://mirrors.ustc.edu.cn/qtproject/online/qtsdkrepository/windows_x86/root/qt/