Fixing vllm build (#6433)

* Fixing torch version for vllm

build.py

@@ -1366,9 +1366,11 @@ def dockerfile_prepare_container_linux(argmap, backends, enable_gpu, target_mach
     if "vllm" in backends:
         # [DLIS-5606] Build Conda environment for vLLM backend
         # Remove Pip install once vLLM backend moves to Conda environment.
+        # [DLIS-5650] Pre-installing torch 2.0.1, since vllm 0.2
+        # requires torch >= 2.0.0, but it doesn't work with torch 2.1.0.
         df += """
 # vLLM needed for vLLM backend
-RUN pip3 install vllm=={}
+RUN pip3 install torch==2.0.1 vllm=={}
 """.format(
             TRITON_VERSION_MAP[FLAGS.version][7]
         )