retropie-on-ubuntu14.04

Setting up ubuntu x86 14.04 LTS for retropie 4.9.8 (at time of writing)

The "Additional drivers" feature in ubuntu 14.04 has the drivers for really old model AGP cards, while 16.04 LTS does not.
Without graphics drivers, old AGP cards will typically not render emulationstation properly and the graphics will appear as blank boxes. This means that later versions of ubuntu (e.g. 16.04 LTS) are not suited for such old hardware to run retropie - if at all.

The issue is that gcc-4.8 causes emulationstation compilation to fail. Problem is fixed in gcc-4.9, so you have to install gcc-4.9 alongside 4.8 and then get ubuntu to use it by default.

Anyway, I managed to get retropie build to work on 14.04, and here's what you do as root user or in sudo:

(add toolchain repository to lubuntu and install gcc and g++ 4.9)
add-apt-repository ppa:ubuntu-toolchain-r/test
apt-get update
apt-get install gcc-4.9 g++-4.9

(shouldn't really need to do this bit on a fresh OS install - here for completeness)
update-alternatives --remove-all gcc
update-alternatives --remove-all g++

(update the priorities for which gcc to use)
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 10
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 20

(update the priorities for which g++ to use)
update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 10
update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 20

(link cc and c++ to gcc and g++ - you can ignore the warnings)
update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
update-alternatives --set cc /usr/bin/gcc
update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
update-alternatives --set cc /usr/bin/g++

(configs the default commands for gcc and g++ - you can now see the alternatives available)
update-alternatives --config gcc
update-alternatives --config g++

After this emulationstation will build properly as per instructions.