added arch=$arch to scons arguments for per-device testing of cuda backend
added arch=$arch to scons arguments for per-device testing of cuda backend

UIKit0/thrust,UIKit0/thrust,levendlee/thrust,Vishwa07/thrust,rdmenezes/thrust,hemmingway/thrust,allendaicool/thrust,allendaicool/thrust,bfurtaw/thrust,google-code-export/thrust,malenie/thrust,h1arshad/thrust,julianromera/thrust,malenie/thrust,julianromera/thrust,rdmenezes/thrust,rdmenezes/thrust,bfurtaw/thrust,google-code-export/thrust,lishi0927/thrust,h1arshad/thrust,allendaicool/thrust,levendlee/thrust,rdmenezes/thrust,lishi0927/thrust,julianromera/thrust,h1arshad/thrust,lishi0927/thrust,malenie/thrust,google-code-export/thrust,UIKit0/thrust,hemmingway/thrust,hemmingway/thrust,Vishwa07/thrust,allendaicool/thrust,google-code-export/thrust,hemmingway/thrust,lishi0927/thrust,UIKit0/thrust,bfurtaw/thrust,levendlee/thrust,Vishwa07/thrust,Vishwa07/thrust,h1arshad/thrust,malenie/thrust,julianromera/thrust,levendlee/thrust,bfurtaw/thrust