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

A similar fix has been applied in the upstream project: opscode/dep-selector-libgecode#33

/cc @opscode/client-engineers @opscode/release-engineers