stagefright: Additional fixes for extended offload support

 * Fix compilation with debug enabled
 * Allow FLAC offload to be enabled independent of QCOM_HARDWARE,
   tested with the Nexus 5X and is working!
 * Disable the FLACExtractor if offload is enabled since it can
   only output decoded PCM. This will force FFMPEG to be used,
   which does everything we need for FLAC offload

Change-Id: I7d71c153a6a6ea7df8e32bc73f5cbe9f51cdcf64