Fix pacstrap -P

Fix pacstrap -P, where the tmp edited version of pacman.conf is copied to the target, with undesirable edits and readonly root permission.

Fixes #70

pacstrap.in

@@ -142,9 +142,8 @@ shift
 tmpfile="$(mktemp -t pacman.conf.XXXX)"
 cp "$pacman_config" "$tmpfile"
 sed -i 's/^DownloadUser/#&/' "$tmpfile"
-pacman_config="$tmpfile"
 
-pacman_args+=("$pacmode" "${@:-base}" --config="$pacman_config" --disable-sandbox)
+pacman_args+=("$pacmode" "${@:-base}" --config="$tmpfile" --disable-sandbox)
 
 if (( ! hostcache )); then
   pacman_args+=(--cachedir="$newroot/var/cache/pacman/pkg")