[COOK-4706] Make nameserver search fully configurable

I have added a chef_search attribute. I put it inside the recipe to allow backwards compatibility in case users were overriding the server_role attribute in a wrapper cookbook. I also pulled in some test files from the build-essential cookbook, with a minor fix to the Gemfile to fix a dependency problem.
@cwebberOps You changed the solaris2 platform to solaris in your 1.2.0 release commit, but those are actually different platforms. If you want to declare explicit solaris support, add it to the list.