Define a CI slave for performance

Slave build performances

Currently the build on the Jenkins slaves is about the same time than on a dev laptop.

=> we can make better !

It's true that a big part of the Jenkins slave are poor hardware (the dwarf).

Before taking any decision, we should probably do some profiling to see exactly what are the real impacting factors :

test build on a bigger CPU (like Octo)
use RAMFS to speedup I/O
tweak compile options ?
test on big RackSpace VMs

=> based on that we will be able to define what kind of Build slaves we need

(then we will have to see what we can host internaly and what must be external)