ui-macos/bits/runpython.do: skip ppc64 architecture.

I don't have a Mac that can build it.  Hopefully ppc will run fine on ppc64.

ui-macos/bits/runpython.do

@@ -4,6 +4,7 @@ ARCHES=""
 printf "Platforms: "
 for d in /usr/libexec/gcc/darwin/*; do
     PLAT=$(basename "$d")
+    [ "$PLAT" != "ppc64" ] || continue  # fails for some reason on my Mac
     ARCHES="$ARCHES -arch $PLAT"
     printf "$PLAT "
 done