[Validator] Stub Fourflusher destination in specs

spec/unit/validator_spec.rb

@@ -392,6 +392,7 @@ module Pod
       end
 
       it 'checks if xcodebuild returns a successful status code' do
+        Fourflusher::SimControl.any_instance.stubs(:destination).returns(['-destination', 'id=XXX'])
         Validator.any_instance.unstub(:xcodebuild)
         validator = Validator.new(podspec_path, SourcesManager.master.map(&:url))
         validator.stubs(:check_file_patterns)