Allow preferences for classes in the 'setup' area

Author: fredden

setup/src/Magento/Setup/Console/Command/DiCompileCommand.php

@@ -399,6 +399,7 @@ private function getOperationsConfiguration(
             OperationFactory::AREA_CONFIG_GENERATOR => [
                 $compiledPathsList['application'],
                 $compiledPathsList['library'],
+                $compiledPathsList['setup'],
                 $compiledPathsList['generated_helpers'],
             ],
             OperationFactory::INTERCEPTION_CACHE => [