ci: fix build cache (#950)

diff --git a/images/designate/Earthfile b/images/designate/Earthfile
index 21d8973..65e5af8 100644
--- a/images/designate/Earthfile
+++ b/images/designate/Earthfile
@@ -1,6 +1,5 @@
 VERSION 0.7
 
-ARG --global REGISTRY=ghcr.io/vexxhost/atmosphere
 ARG --global PROJECT=designate
 ARG --global RELEASE=2023.2
 ARG --global PROJECT_REF=2c817b3d7f01de44023f195c6e8de8853683a54a
@@ -16,6 +15,7 @@
   COPY +build/venv /var/lib/openstack
   DO ../+APT_INSTALL \
     --PACKAGES "bind9utils"
+  ARG REGISTRY=ghcr.io/vexxhost/atmosphere
   SAVE IMAGE --push \
     ${REGISTRY}/${PROJECT}:${RELEASE} \
     ${REGISTRY}/${PROJECT}:${PROJECT_REF}