Added a small fix to exclude the AMD optimized assembly file from being included...

Added a small fix to exclude the AMD optimized assembly file from being included in the compile.
I don't particular like the approach, which basically tries to exclude the file based on
NOT being in a list of arches. This, IMHO, is backwards, it should be a list of AMD arches
instead. "Better to light a candle, than to curse the darkness", is apropo here. But since I don't
have an exhaustive list of what those arches could be, I leave as-is for now.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@38187 65c4cc65-6c06-0410-ace0-fbb531ad65f3