Fix 3h timeout: use kernel overlay in buildah (fuse-overlayfs made commit crawl), fresh cache volume

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.forgejo/workflows/build.yml

@@ -17,6 +17,7 @@ jobs:
   build:
     name: Build ${{ matrix.image_name }}
     runs-on: ubuntu-latest
+    timeout-minutes: 280
     strategy:
       fail-fast: false
       matrix:
@@ -40,9 +41,9 @@ jobs:
       # buildah container instead — the same tool Bazzite itself is built with.
       - name: Build and push with buildah
         run: |
-          docker volume create kamos-buildah-cache >/dev/null 2>&1 || true
+          docker volume create kamos-buildah >/dev/null 2>&1 || true
           tar -cf - . | docker run --rm -i --privileged \
-            -v kamos-buildah-cache:/var/lib/containers \
+            -v kamos-buildah:/var/lib/containers \
             -e IMAGE="${IMAGE}" \
             -e DATE_TAG="${DATE_TAG}" \
             -e BASE_IMAGE="${{ matrix.base_image }}" \
@@ -51,6 +52,10 @@ jobs:
             quay.io/buildah/stable:latest \
             bash -c '
               set -euo pipefail
+              # Use the fast kernel overlay driver instead of fuse-overlayfs
+              # (we are privileged, so this works — and is ~50x faster on
+              # the millions of small files in the OSTree base)
+              sed -i "s|^mount_program|#mount_program|" /etc/containers/storage.conf || true
               mkdir -p /src && tar -xf - -C /src && cd /src
               buildah build -f Containerfile \
                 --build-arg BASE_IMAGE="$BASE_IMAGE" \