build using system nvtt (Closes: #794562)
Note that this requires the recently uploaded nvidia-texture-tools 2.1.2~dfsg-4.
Also note that cmake was only used to build bundled nvtt, so it is also removed from build depends.
Note that this requires the recently uploaded nvidia-texture-tools 2.1.2~dfsg-4.
Also note that cmake was only used to build bundled nvtt, so it is also removed from build depends.