fixup! WIP update ci

Author: willcl-ark

.github/workflows/build.yml

@@ -22,6 +22,8 @@ jobs:
       matrix:
         version: ['29.1', '30.0rc1']
       fail-fast: false
+    env:
+      USERNAME: bitcoin
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -33,10 +35,12 @@ jobs:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Setup Cachix
-        uses: cachix/cachix-action@v14
+        uses: cachix/cachix-action@v15
         with:
           name: bitcoin-core-docker
-          skipPush: true
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
+      - uses: extractions/setup-just@v3
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
@@ -45,14 +49,14 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/v')
         uses: docker/login-action@v3
         with:
-          username: bitcoin
+          username: ${{ env.USERNAME }}
           password: ${{ secrets.DOCKER_HUB_PASSWORD }}
 
       - name: Build images
         run: |
-          nix run .#build-all-${{ matrix.version }}
+          just build-all ${{ matrix.version }}
 
       - name: Push images
         if: startsWith(github.ref, 'refs/tags/v')
         run: |
-          nix run .#push-${{ matrix.version }}
+          just push ${{ matrix.version }} docker.io/${{ env.USERNAME }}