If a short-path cannot be created, fallback to absolute path, even though it's more verbose.

lib/cmock_config.rb

@@ -81,7 +81,11 @@ class CMockConfig
       require 'pathname'
       includes1 = options[:includes_c_post_header] || []
       includes2 = options[:unity_helper_path].map do |path|
-        Pathname(File.expand_path(path)).relative_path_from(Pathname(File.expand_path(options[:mock_path]))).to_s
+        begin
+          Pathname(File.expand_path(path)).relative_path_from(Pathname(File.expand_path(options[:mock_path]))).to_s
+        rescue
+          path
+        end
       end
       options[:includes_c_post_header] = (includes1 + includes2).uniq
     end