[Cin]respin of libaom build options patch to use NASM

I tested it on ubuntu 16.04 + updated nasm and it seems to build fine (with libaom 3.8.0) Dear Phyllis, can you test it again? I hope it will work in other cases too (this is supported option, after all), and you (and anyone else) will able to build cingg on old Ubuntu out of the box.