Set travis to use cmake explicitly
Set travis to use cmake explicitly

* I thought it was using cmake already, but it was using make. Whoops!
* This will make it easier to add a release target in travis in future
  though, which is a nice bonus.

victor-moya/renderdoc,moradin/renderdoc,Velro/renderdoc,michaelrgb/renderdoc,Lssikkes/renderdoc,adrianbu/renderdoc,victor-moya/renderdoc,Anteru/renderdoc,Lssikkes/renderdoc,moradin/renderdoc,cgmb/renderdoc,Lssikkes/renderdoc,Zorro666/renderdoc,googlestadia/renderdoc,moradin/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,Anteru/renderdoc,victor-moya/renderdoc,Zorro666/renderdoc,TurtleRockStudios/renderdoc_public,victor-moya/renderdoc,etnlGD/renderdoc,googlestadia/renderdoc,michaelrgb/renderdoc,Anteru/renderdoc,cgmb/renderdoc,Zorro666/renderdoc,moradin/renderdoc,moradin/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,Velro/renderdoc,Zorro666/renderdoc,Yours3lf/renderdoc,Yours3lf/renderdoc,victor-moya/renderdoc,etnlGD/renderdoc,cgmb/renderdoc,cgmb/renderdoc,googlestadia/renderdoc,TurtleRockStudios/renderdoc_public,Yours3lf/renderdoc,TurtleRockStudios/renderdoc_public,baldurk/renderdoc,michaelrgb/renderdoc,adrianbu/renderdoc,victor-moya/renderdoc,Anteru/renderdoc,baldurk/renderdoc,etnlGD/renderdoc,adrianbu/renderdoc,adrianbu/renderdoc,Yours3lf/renderdoc,Velro/renderdoc,Yours3lf/renderdoc,etnlGD/renderdoc,Velro/renderdoc,Anteru/renderdoc,baldurk/renderdoc,Lssikkes/renderdoc,TurtleRockStudios/renderdoc_public,Anteru/renderdoc,adrianbu/renderdoc,Yours3lf/renderdoc,googlestadia/renderdoc,etnlGD/renderdoc,Velro/renderdoc,michaelrgb/renderdoc,cgmb/renderdoc,googlestadia/renderdoc,Velro/renderdoc,googlestadia/renderdoc,Zorro666/renderdoc,Lssikkes/renderdoc,moradin/renderdoc,adrianbu/renderdoc,baldurk/renderdoc,michaelrgb/renderdoc,etnlGD/renderdoc,Anteru/renderdoc,Lssikkes/renderdoc,Zorro666/renderdoc