Build arbitration graphs base image using current repo state

The ghcr version of the image might not represent the current state of
the library and possibly does not even exist for the version of a dev
branch.

.github/workflows/run-unit-tests.yaml

@@ -15,6 +15,14 @@ jobs:
         run: |
           cat version >> $GITHUB_ENV
 
+      - name: Build and core library Docker image using current repo state
+        uses: docker/build-push-action@v6
+        with:
+          push: false
+          tags: |
+            ghcr.io/kit-mrt/arbitration_graphs:${{ env.VERSION }}
+          target: install
+
       - name: Build core library unit test Docker image
         uses: docker/build-push-action@v6
         with: