Set ports/archive as appropriate for default mirror - should fix

autopkgtests.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.495) UNRELEASED; urgency=medium
+
+  * Set ports/archive as appropriate for default mirror - should fix
+    autopkgtests.
+
+ -- Iain Lane <iain.lane@canonical.com>  Wed, 31 Jan 2018 09:37:44 +0000
+
 livecd-rootfs (2.494) bionic; urgency=medium
 
   * Run subiquity on any serial consoles that the user told systemd

live-build/auto/config

@@ -30,7 +30,11 @@ if [ -z "$MIRROR" ]; then
 		*.buildd)		MIRROR=http://ftpmaster.internal/ubuntu/
 					SEEDMIRROR=http://archive-team.internal/seeds/
 					;;
-		*)			MIRROR=http://archive.ubuntu.com/ubuntu/ ;;
+		*)			case $ARCH in
+						i386|amd64) MIRROR=http://archive.ubuntu.com/ubuntu/ ;;
+						*) MIRROR=http://ports.ubuntu.com/ubuntu-ports ;;
+					esac
+					;;
 	esac
 fi