switch amd64 to the arch variable

live-build/auto/config

@@ -485,7 +485,7 @@ case $IMAGEFORMAT in
 			# We need to look in two places for the gadget tree:
 			# - Launchpad hosted gadgets will be in the snap-gadget repo
 			# - Github hosted gadgets are mirrored into a github-mirror repo
-			git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/snap-$MODEL -b $BRANCH config/$PREFIX-gadget || git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/github-mirror -b $BRANCH config/$PREFIX-gadget || git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/github-mirror-amd64 -b $BRANCH config/$PREFIX-gadget
+			git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/snap-$MODEL -b $BRANCH config/$PREFIX-gadget || git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/github-mirror -b $BRANCH config/$PREFIX-gadget || git clone git://git.launchpad.net/~canonical-foundations/snap-$MODEL/+git/github-mirror-$ARCH -b $BRANCH config/$PREFIX-gadget
 
 			echo "IMAGEFORMAT=$IMAGEFORMAT" >> config/common
 			echo "SUITE=$SUITE" >> config/common