Install g++ 4.8 on Ubuntu 12.04

Ubuntu12.04-g++4.8

*Add the toolchain/test PPA*
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install g++-4.8
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 50

*If you ever want to update symlinks for a future version:*
sudo rm /usr/bin/g++
sudo ln -s /usr/bin/g++-4.XXX /usr/bin/g++

*Check version number*
g++ --version

I'd add -y for every apt command to make sure it runs on an automated CI.

sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
sudo apt-get update -y
sudo apt-get install -y g++-4.8
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 50