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
Merge pull request #298 from opscode/schisamo/windows-tar-fix

Configure Window’s environments to use `bsdtar`