Add possibility to store utility targets in tmp dir

[tadatuta]

We have possibility to define which targets needed for the user and which are just for needs of building process. So it'd great to store utility targets into .enb/tmp/ folder not to mess with useful build results.

[narqo]

It would be great if the path to tmp dir could be set to somewhere outside of the project dir. For example if we use enb as a middleware builder with node application server, which is run as a service by some system supervisor, like init, currently there are some problems with the rights for writing in the tmp dir

[andre487]

+1