Fix detection of active GPU

[Windwoes]

Fixes detection of active GPU by using nvidia's prime-select query command

[bauca]

Hi @FROGbots-4634 , your contribution is much appreciated, I am just curious to ask you whether this implementation would change the current requirements? I see that you are using "prime-select" instead of "glxinfo".

[Windwoes]

Hi, yes, I think that mesa-utils is not required with this change. Btw, my machine is a Dell Latitude E6530 with an Nvidia NVS 5200M on Ubuntu 18.04.

[bauca]

I can't test myself since I'm not actively using my old laptop anymore, however, I'll leave it open until another person can test and confirm that mesa-utils is not required anymore.