Configure Window’s environments to use `bsdtar`

The Ruby DevKit ships with `bsdtar` instead of `tar`. This change just ensures the environment is configured to use it.

Up until this point we have gotten lucky as our ChefDK builds build Chef first which in turn copies `bsdtar.exe` over to `tar.exe`:
https://github.com/opscode/omnibus-chef/blob/master/config/software/chef.rb#L61

/cc @opscode/client-engineers @opscode/release-engineers