ci: fix build cache (#950)

diff --git a/images/openvswitch/Earthfile b/images/openvswitch/Earthfile
index b72a75d..35c3b2e 100644
--- a/images/openvswitch/Earthfile
+++ b/images/openvswitch/Earthfile
@@ -1,6 +1,5 @@
 VERSION 0.7
 
-ARG --global REGISTRY=ghcr.io/vexxhost/atmosphere
 ARG --global SERIES=3.1
 ARG --global VERSION=3.1.0-65
 
@@ -9,6 +8,7 @@
   LABEL org.opencontainers.image.source=https://github.com/vexxhost/atmosphere
   DO ../+DNF_INSTALL --PACKAGES "centos-release-nfv-openvswitch.noarch"
   DO ../+DNF_INSTALL --PACKAGES "openvswitch${SERIES}-${VERSION}.el9s iptables"
+  ARG REGISTRY=ghcr.io/vexxhost/atmosphere
   SAVE IMAGE --push \
     ${REGISTRY}/openvswitch:${SERIES} \
     ${REGISTRY}/openvswitch:${VERSION}