version ChefDK with a static version number

Using a static version will make it easier to promote binary artifacts. 
However, it comes with the cost of having to managing bumping the version 
as part of the normal development cycle.

config/projects/chefdk.rb

@@ -20,10 +20,7 @@
 homepage "https://www.chef.io"
 
 build_iteration 1
-build_version do
-  source :git, from_dependency: 'chefdk'
-  output_format :semver
-end
+build_version '0.8.0'
 
 if windows?
   # NOTE: Ruby DevKit fundamentally CANNOT be installed into "Program Files"