Bullseye alongside Bookworm (#61)

* revert to bullseye.

* add bookworm.

* add bookworm to variants.

* include xf86-video-dummy because the remote git instance is offline.

* fix configure.

.github/workflows/build_variants.yml

@@ -19,7 +19,12 @@ jobs:
     strategy:
       matrix:
         include:
+          - variant: bookworm
+            dockerfile: Dockerfile.bookworm
           - variant: nvidia
+            dockerfile: Dockerfile.nvidia
+          - variant: nvidia_bookworm
+            dockerfile: Dockerfile.nvidia.bookworm
 
     steps:
       - name: Checkout repository
@@ -42,7 +47,7 @@ jobs:
         uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
         with:
           context: .
-          file: Dockerfile.${{ matrix.variant }}
+          file: ${{ matrix.dockerfile }}
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}