x86_64 is used as a baseline: the "x86_64" entry, whatever status it has,
is transformed into "all", and then the other entries in ARCHITECTURES
either dropped or rearranged appropriately.
uname -p is "x86" even on x86_gcc2 installs, and won't handle secondary
architecture properly anyway. Use haikuports provided
$targetArchitecture, which I think is the right thing to do here.