infra: move docker workflow into gentoo-utils workflow

infra: add build job to CI

.gitea/workflows/docker.yml

@@ -1,42 +0,0 @@
-name: Build gentoo-utils docker image
-
-on:
-  push:
-    branches:
-      - master
-    paths:
-      - '.docker/Dockerfile'
-  pull_request:
-    paths:
-      - '.docker/Dockerfile'
-  workflow_dispatch:
-
-
-jobs:
-  build-docker:
-    runs-on: ubuntu-latest
-
-    steps:
-      -
-        name: Checkout repo
-        uses: actions/checkout@v4
-
-      -
-        name: Set up Docker buildx
-        uses: docker/setup-buildx-action@v3
-
-      -
-        name: Log in to Github Container Registry
-        uses: docker/login-action@v3
-        with:
-          registry: git.epenguin.net
-          username: ${{ gitea.actor }}
-          password: ${{ secrets.CI_TOKEN }}
-
-      -
-        name: Build and push
-        uses: docker/build-push-action@v6
-        with:
-          push: true
-          tags: git.epenguin.net/${{ gitea.repository }}:latest
-          context: "{{defaultContext}}:.docker"

.gitea/workflows/gentoo-utils.yml

@@ -0,0 +1,59 @@
+name: Gentoo Utils
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  build-docker:
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    steps:
+      -
+        name: Checkout repo
+        uses: actions/checkout@v5
+        with:
+          fetch-depth: 0
+
+      - name: Check for changes before building
+        id: image-changes
+        run: |
+          if git diff --name-only ${{ gitea.event.before }} ${{ gitea.sha }} | grep -q '^\.docker/'; then
+            echo "changes_detected=true" >> $GITEA_OUTPUT
+          else
+            echo "changes_detected=false" >> $GITEA_OUTPUT
+          fi
+      -
+        name: Set up Docker buildx
+        if: steps.docker-changes.outputs.changes_detected == 'true'
+        uses: docker/setup-buildx-action@v3
+
+      -
+        name: Log in to Github Container Registry
+        if: steps.docker-changes.outputs.changes_detected == 'true'
+        uses: docker/login-action@v3
+        with:
+          registry: git.epenguin.net
+          username: ${{ vars.CI_BOT_USERNAME }}
+          password: ${{ secrets.CI_BOT_TOKEN }}
+
+      -
+        name: Build and push
+        if: steps.docker-changes.outputs.changes_detected == 'true'
+        uses: docker/build-push-action@v6
+        with:
+          push: true
+          tags: git.epenguin.net/${{ gitea.repository }}:latest
+          context: "{{defaultContext}}:.docker"
+
+  build:
+    runs-on: gentoo-utils
+    needs: build-docker
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v5
+
+      - name: build and check
+        run: ./check.sh