build-arg for ubuntu was added to alpine in readme

Signed-off-by: Rui Yang <[email protected]>

Author: Rui Yang

README.md

@@ -322,8 +322,8 @@ will stop the build.
 Run the tests with the following commands for both `alpine` and `ubuntu` images:
 
 ```sh
-docker build -t docker-image-resource -f dockerfiles/alpine/Dockerfile --build-arg base_image=ubuntu:latest .
-docker build -t docker-image-resource -f dockerfiles/ubuntu/Dockerfile .
+docker build -t docker-image-resource -f dockerfiles/alpine/Dockerfile .
+docker build -t docker-image-resource -f dockerfiles/ubuntu/Dockerfile --build-arg base_image=ubuntu:latest .
 ```
 
 To use the newly built image, push it to a docker registry that's accessible to