Allow the arch= command line variable to take a list of values. Implement it with -gencode instead of -arch.
Allow the arch= command line variable to take a list of values.
Implement it with -gencode instead of -arch.

Fixes #164

zhenglaizhang/thrust,egaburov/thrust,thrust/thrust,dachziegel/thrust,arnabgho/thrust,sarvex/thrust,zeryx/thrust,andrewcorrigan/thrust-multi-permutation-iterator,arnabgho/thrust,sdalton1/thrust,raygit/thrust,mohamed-ali/thrust,zeryx/thrust,jaredhoberock/thrust,thrust/thrust,thvasilo/thrust,zhenglaizhang/thrust,xiongzhanblake/thrust,marksantos/thrust,Ricardo666666/thrust,xiongzhanblake/thrust,jaredhoberock/thrust,Ricardo666666/thrust,xiongzhanblake/thrust_src,andrewcorrigan/thrust-multi-permutation-iterator,marksantos/thrust,mohamed-ali/thrust,andrewcorrigan/thrust-multi-permutation-iterator,GrimDerp/thrust,sdalton1/thrust,dachziegel/thrust,dachziegel/thrust,thrust/thrust,raygit/thrust,raygit/thrust,jaredhoberock/thrust,sdalton1/thrust,thvasilo/thrust,xiongzhanblake/thrust_src,jaredhoberock/thrust,Ricardo666666/thrust,thvasilo/thrust,xiongzhanblake/thrust,GrimDerp/thrust,egaburov/thrust,sarvex/thrust,thrust/thrust,zhenglaizhang/thrust,zeryx/thrust,xiongzhanblake/thrust_src,thrust/thrust,mohamed-ali/thrust,egaburov/thrust,arnabgho/thrust,marksantos/thrust,GrimDerp/thrust,jaredhoberock/thrust,sarvex/thrust