Try cleanups before ipex install in docker.

docker/Dockerfile

@@ -13,6 +13,7 @@ ENV PIP_EXTRA_INDEX_URL https://pytorch-extension.intel.com/release-whl/stable/x
 
 # We need to override some too-old dependencies on ipex-llm
 RUN cd /app && python3 -m pip install -U pip && python3 -m pip install . && \
+    python3 -m pip cache purge && \
     python3 -m pip install torch==2.1.0.post3 torchvision==0.16.0.post3 torchaudio==2.1.0.post3 intel-extension-for-pytorch==2.1.40+xpu oneccl_bind_pt==2.1.400+xpu && \
     python3 -m pip install numpy==1.26.4 && \
     python3 -m pip install transformers==4.41.2 trl