Simplify build system

Author: benjeffery

.github/workflows/build-core.yml

@@ -0,0 +1,58 @@
+name: Build core site
+
+on:
+  workflow_call:
+
+jobs:
+  cancel-superseded:
+    name: Cancel superseded
+    runs-on: ubuntu-24.04
+    steps:
+        - name: Cancel Previous Runs
+          uses: styfle/[email protected]
+          with:
+            access_token: ${{ github.token }}
+
+  build-core-site:
+    needs: cancel-superseded
+    name: Build core site
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Cancel Previous Runs
+        uses: styfle/[email protected]
+        with:
+          access_token: ${{ github.token }}
+
+      - name: Checkout
+        uses: actions/[email protected]
+
+      - name: Set up Ruby 2.7
+        uses: ruby/[email protected]
+        with:
+          ruby-version: '2.7'
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+
+      - uses: actions/[email protected]
+        with:
+          node-version: 14
+          cache: 'npm'
+
+      - name: Install deps
+        run: npm ci
+
+      - name: Build site
+        run: GITHUB_TOKEN=${{ github.token }} grunt build
+
+      - name: Debug
+        run: |
+          cat Gemfile.lock
+          bundle info jekyll
+          bundle info jekyll-theme-cayman
+          ls
+          cat dist/index.html
+
+      - name: Upload built site
+        uses: actions/[email protected]
+        with:
+          name: core-site
+          path: dist/*