Temp commit with hashFiles debug information

.github/workflows/build-docker.yml

@@ -81,6 +81,14 @@ jobs:
           platform=${{ matrix.platform }}
           echo "PLATFORM_TUPLE=${platform//\//-}" >> $GITHUB_ENV
 
+      - name: Visualise cache key contents
+        run: |
+          # Run the script that the runner uses to produce the value used by `hashFiles()`
+          # Arguments to `hashFiles` are passed in as the `patterns` environment variable
+          # separated by newlines.
+          export patterns=$'Dockerfile\ncrates/**\nCargo.toml\nCargo.lock'
+          /home/runner/runners/2.321.0/externals/node20/bin/node "/home/runner/runners/2.321.0/bin/hashFiles"
+
       - name: Docker apt & pip caches
         uses: actions/cache@v4
         id: docker-caches