update

Author: yi.wu

paddle/scripts/docker/README.md

@@ -108,7 +108,10 @@ This command mounts the source directory on the host into `/paddle` in the conta
 Users can specify the following Docker build arguments with either "ON" or "OFF" value:
 - `WITH_GPU`: ***Required***. Generates NVIDIA CUDA GPU code and relies on CUDA libraries.
 - `WITH_AVX`: ***Required***. Set to "OFF" prevents from generating AVX instructions. If you don't know what is AVX, you might want to set "ON".
-- `WITH_TEST`: ***Optional, default OFF***. Build unit tests binaries.
+- `WITH_TEST`: ***Optional, default OFF***. Build unit tests binaries. Once you've built the unit tests, you can run these test manually by the following command:
+  ```bash
+    docker run -v $PWD:/paddle -e "WITH_GPU=OFF" -e "WITH_AVX=ON" paddle:dev sh -c "cd /paddle/build; make coverall"
+  ```
 - `RUN_TEST`: ***Optional, default OFF***. Run unit tests after building. You can't run unit tests without building it.
 
 ### Build the Production Docker Image