CI: Do build stage in separate pipeline from sync

.gitlab-ci.yml

@@ -5,6 +5,8 @@ stages:
 
 'Sync Portage':
   stage: 'sync'
+  rules:
+    - if: '$BUILD_IMAGE != "1"'
   script:
     # Config
     - 'git config --global user.name "Nest CI"'
@@ -34,13 +36,14 @@ stages:
     - 'git add .'
     - 'git commit -m "$(date -I) snapshot"'
     - 'git remote set-url origin git@gitlab.james.tl:nest/gentoo/portage.git'
-    - 'git push -o ci.skip origin "HEAD:${CI_COMMIT_BRANCH}"'
+    - 'git push -o ci.variable="BUILD_IMAGE=1" origin "HEAD:${CI_COMMIT_BRANCH}"'
 
 'Build Image':
-  stage: 'build'
   image: '${CI_REGISTRY}/nest/tools/buildah:${CI_HOST_CPU}'
+  stage: 'build'
+  rules:
+    - if: '$BUILD_IMAGE == "1"'
   script:
-    - 'git pull'
     - 'buildah login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" "$CI_REGISTRY"'
     - 'buildah bud --pull -t "$CI_REGISTRY_IMAGE" -f .Containerfile .'
     - 'buildah push "$CI_REGISTRY_IMAGE"'