enable bnb tests

Signed-off-by: jiqing-feng <jiqing.feng@intel.com>

Author: jiqing-feng

.github/workflows/test_ipex.yml

@@ -37,6 +37,7 @@ jobs:
           pip install --upgrade pip
           pip install torch==${{ matrix.torch-version }} torchaudio torchvision --extra-index-url https://download.pytorch.org/whl/cpu
           pip install .[ipex,tests] transformers[testing]==${{ matrix.transformers-version }} intel_extension_for_pytorch==${{ matrix.torch-version }}
+          git clone --branch multi-backend-refactor https://github.com/bitsandbytes-foundation/bitsandbytes.git && cd bitsandbytes/ && pip install .
 
       - name: Assert versions
         run: |