Please use josn board manager script from http://www.arducam.com/downloads/ESP8266_UNO/package_ArduCAM_index.json to download ESP8266 UNO board support files.
ArduCAM/ArduCAM_ESP8266_UNO
This Arduino IDE for ArduCAM ESP8266 UNO Board with Integrated ArduCAM Library and Examples
CLGPL-2.1