Pull the Arch image from GitHub's registry

A unit test run stopped before it began: Docker Hub refused to hand out
archlinux:latest, "You have reached your unauthenticated pull rate
limit". GitHub's runners share addresses, so the limit is not ours to
stay under.

Arch publishes the same image as ghcr.io/archlinux/archlinux, which has
no such limit from a runner. The three workflow containers and the ISO
build's own container pull it from there.

.github/workflows/install-test.yml

@@ -50,7 +50,7 @@ jobs:
           sudo chmod 0666 /dev/kvm
           docker run --rm --device /dev/kvm -v "$PWD:/w" -w /w \
             -e OMARCHY_INTEGRATION_DISK_CACHE=none \
-            archlinux:latest bash -euo pipefail -c '
+            ghcr.io/archlinux/archlinux:latest bash -euo pipefail -c '
               # pacman 7 fails every sync on a kernel without Landlock, which
               # these runners have; builder/build-iso.sh does the same.
               if ! grep -qw landlock /sys/kernel/security/lsm 2>/dev/null; then

.github/workflows/nightly-build.yml

@@ -132,7 +132,7 @@ jobs:
           sudo chmod 0666 /dev/kvm
           docker run --rm --device /dev/kvm -v "$PWD:/w" -w /w \
             -e OMARCHY_INTEGRATION_DISK_CACHE=none \
-            archlinux:latest bash -euo pipefail -c '
+            ghcr.io/archlinux/archlinux:latest bash -euo pipefail -c '
               # pacman 7 fails every sync on a kernel without Landlock, which
               # these runners have; builder/build-iso.sh does the same.
               if ! grep -qw landlock /sys/kernel/security/lsm 2>/dev/null; then

.github/workflows/unit-test.yml

@@ -33,7 +33,7 @@ jobs:
         run: |
           docker run -d --name unit --privileged --cgroupns=host \
             -v /sys/fs/cgroup:/sys/fs/cgroup:rw --tmpfs /run --tmpfs /tmp:exec \
-            -v "$PWD:/src:ro" archlinux:latest bash -c '
+            -v "$PWD:/src:ro" ghcr.io/archlinux/archlinux:latest bash -c '
               systemctl mask getty.target console-getty.service \
                 systemd-udev-trigger.service systemd-udevd.service \
                 systemd-vconsole-setup.service

bin/omarchy-iso-make

@@ -166,7 +166,7 @@ if ! docker version &>/dev/null; then
   DOCKER=(sudo docker)
 fi
 
-"${DOCKER[@]}" run "${DOCKER_ARGS[@]}" archlinux/archlinux:latest /$BUILD_SCRIPT
+"${DOCKER[@]}" run "${DOCKER_ARGS[@]}" ghcr.io/archlinux/archlinux:latest /$BUILD_SCRIPT
 
 latest_iso=$(\ls -t "$BUILD_RELEASE_PATH"/*.iso | head -n1)
 iso_ref="${latest_iso%.*}-$OMARCHY_ISO_REF.iso"