ui-macos/bits/runpython.do: report which platforms we're compiling for.

Just as a quick reminder, in case you're building a fat binary and you don't
have all the architectures actually installed.

ui-macos/bits/runpython.do

 exec >&2
 redo-ifchange runpython.c
 ARCHES=""
+printf "Platforms: "
 for d in /usr/libexec/gcc/darwin/*; do
-    ARCHES="$ARCHES -arch $(basename $d)"
+    PLAT=$(basename "$d")
+    ARCHES="$ARCHES -arch $PLAT"
+    printf "$PLAT "
 done
+printf "\n"
 gcc $ARCHES \
 	-Wall -o $3 runpython.c \
 	-I/usr/include/python2.5 \