在windows store里安装的“Ubuntu”，换了阿里源
在运行sudo apt install g++时出现如下报错信息：
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
g++ : Depends: g++-5 (>= 5.3.1-3~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
并且按照中间说的 g++-5 递归安装下去就会GG
