ci: fix build cache (#950)

diff --git a/images/neutron/Earthfile b/images/neutron/Earthfile
index 0776db7..65f1238 100644
--- a/images/neutron/Earthfile
+++ b/images/neutron/Earthfile
@@ -1,6 +1,5 @@
 VERSION 0.7
 
-ARG --global REGISTRY=ghcr.io/vexxhost/atmosphere
 ARG --global PROJECT=neutron
 ARG --global RELEASE=zed
 ARG --global PROJECT_REF=f83e1fd4f057578e1a0b30edae3cc3161f28f5e9
@@ -17,6 +16,7 @@
   COPY +build/venv /var/lib/openstack
   DO ../+APT_INSTALL \
     --PACKAGES "conntrack dnsmasq dnsmasq-utils ebtables ethtool haproxy iproute2 ipset iptables iputils-arping jq keepalived lshw openvswitch-switch strongswan uuid-runtime"
+  ARG REGISTRY=ghcr.io/vexxhost/atmosphere
   SAVE IMAGE --push \
     ${REGISTRY}/${PROJECT}:${RELEASE} \
     ${REGISTRY}/${PROJECT}:${PROJECT_REF}