fix: specify docker in docker

.forgejo/workflows/rust.yml

@@ -61,6 +61,8 @@ jobs:
 
       - name: 🚀 Build with cross
         uses: https://github.com/actions-rs/cargo@v1
+        env:
+          CROSS_CONTAINER_IN_CONTAINER: true
         with:
           use-cross: true
           command: build