FIX: Don't build Hive in assembly unless running Hive tests.

This will make the tests more stable when not running SQL tests.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #439 from pwendell/hive-tests and squashes the following commits:

88a6032 [Patrick Wendell] FIX: Don't build Hive in assembly unless running Hive tests.