Added libgtest-dev to the list of packages installed into the dev build container. (#6784)
Added libgtest-dev to the list of packages installed into the dev build container. (#6784)

Fixes issue [6783](https://github.com/ApolloAuto/apollo/issues/6783)

ApolloAuto/apollo,ApolloAuto/apollo,ycool/apollo,xiaoxq/apollo,jinghaomiao/apollo,wanglei828/apollo,ycool/apollo,ycool/apollo,ApolloAuto/apollo,ycool/apollo,wanglei828/apollo,jinghaomiao/apollo,jinghaomiao/apollo,jinghaomiao/apollo,xiaoxq/apollo,xiaoxq/apollo,jinghaomiao/apollo,wanglei828/apollo,ycool/apollo,ApolloAuto/apollo,ycool/apollo,ApolloAuto/apollo,wanglei828/apollo,wanglei828/apollo,wanglei828/apollo,ApolloAuto/apollo,xiaoxq/apollo,jinghaomiao/apollo,xiaoxq/apollo,xiaoxq/apollo