Chose a stack for an environment

[erothe]

The requirement is to be able to specify which stack to build in each environment. For the moment this is more a test requirement, since the stack does no change across all the environments.

Rigth now, the only difference between environments is the platform target, which is causing a lot of problems. It would be helpfull the compilers installation if we could have two stacks (or more), one for each environment.