change: use CPU Dockerfile for CPU image testing (#11)

Author: laurenyu

buildspec.yml

@@ -54,7 +54,7 @@ phases:
       - build_dir="docker/$FRAMEWORK_VERSION/py$GPU_PY3_VERSION"
       - CPU_PY3_TAG="$FRAMEWORK_VERSION-cpu-py3-$BUILD_ID"
       - GPU_PY3_TAG="$FRAMEWORK_VERSION-gpu-py3-$BUILD_ID"
-      - docker build -f "$build_dir/$gpu_dockerfile" --build-arg py_version=3 -t $PREPROD_IMAGE:$CPU_PY3_TAG .
+      - docker build -f "$build_dir/$cpu_dockerfile" --build-arg py_version=3 -t $PREPROD_IMAGE:$CPU_PY3_TAG .
       - docker build -f "$build_dir/$gpu_dockerfile" --build-arg py_version=3 -t $PREPROD_IMAGE:$GPU_PY3_TAG .
 
       # push images to ecr