For reference extension builds, update book_path to reference the appropriate file location.
am: 8dbd7b96cf

* commit '8dbd7b96cfd667866f992d8bf5252eb8bef29ccc':
  For reference extension builds, update book_path to reference the appropriate file location.

Change-Id: I2555dee5e78998d8e042cfe22c45d9dadd469149