Thanks @Shanshaan, that didn't work for me though (Admittedly I may have changed the "ExtractGameobjectModels" code in gameobject_extract.cpp incorrectly).  New error I'm getting on commit (75ea2f19c47a381cacec2674a5d28fb7d4e72695) is:
Processing Map 1161
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Can't open WorldMapsTransport_Siege_of_Orgrimmar_AllianceTransport_Siege_of_Orgrimmar_Alliance.wdt, err=2!
Can't open WorldMapsTransport_Siege_of_Orgrimmar_HordeTransport_Siege_of_Orgrimmar_Horde.wdt, err=2!
Extracting GameObject models...Read GameObjectDisplayInfo.dbc file...
Handle dbcFile Loaded
First IF loaded File not opened
Fatal error: Cannot find GameObjectDisplayInfo.dbc in archive!