ci: Use chroot isolation and fedora registry

.gitlab-ci.yml

@@ -2,6 +2,8 @@
 # Buildah can't use 'overlay' driver when running inside docker
 variables:
     STORAGE_DRIVER: vfs
+    BUILDAH_FORMAT: 'docker'
+    BUILDAH_ISOLATION: 'chroot'
 
 stages:
     - build
@@ -40,7 +42,7 @@ build_flat_manager_docker_arm64:
     extends: .build_template
     # Workaround: https://gitlab.com/gitlab-org/gitlab-runner/-/issues/27614
     image:
-        name: arm64v8/fedora
+        name: registry.fedoraproject.org/fedora:36-aarch64
         entrypoint: [ '/bin/sh', '-c' ]
     tags:
         - librem5:arm64
@@ -52,7 +54,7 @@ build_flat_manager_docker:
     extends: .build_template
     # Workaround: https://gitlab.com/gitlab-org/gitlab-runner/-/issues/27614
     image:
-        name: fedora:latest
+        name: registry.fedoraproject.org/fedora:36
         entrypoint: [ '/bin/sh', '-c' ]
     tags:
         - librem5