For reference extension builds, update book_path to reference the appropriate...

For reference extension builds, update book_path to reference the appropriate file location. am: 8dbd7b96 am: ce46b862 am: 1d2dbfe4
am: 6598f780

* commit '6598f780':
  For reference extension builds, update book_path to reference the appropriate file location.

Change-Id: I2c0401d746e776a542ca02b97d927836dfeb0e98