Add Gentoo dependencies to CONTRIBUTING.md and mention qtchooser
Add Gentoo dependencies to CONTRIBUTING.md and mention qtchooser

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