make valid_arches conform to arch_to_hostspec()
The arch_to_hostspec()
function in /usr/share/abuild/functions.sh
has all the variables abuild
supports. Lets support all of them in valid_arches
The arch_to_hostspec()
function in /usr/share/abuild/functions.sh
has all the variables abuild
supports. Lets support all of them in valid_arches