Add VLLM_COMMIT cache-bust arg to Dockerfile

Docker was caching the git clone layer because the command
string didn't change. Adding VLLM_COMMIT arg forces cache
invalidation when the source changes.

vllm/Dockerfile

@@ -159,9 +159,11 @@ FROM build-base AS build-vllm
 # vLLM version/branch to build
 # Using our Gitea fork (sweetapi.com/biondizzle/vllm) on the cmm branch
 ARG VLLM_REF=cmm
+ARG VLLM_COMMIT=latest
 # Install ccache for faster compilation
 RUN apt-get update && apt-get install -y ccache
-RUN git clone https://sweetapi.com/biondizzle/vllm.git
+RUN git clone https://sweetapi.com/biondizzle/vllm.git && \
+    echo "VLLM_COMMIT=${VLLM_COMMIT}" > /tmp/vllm_commit_cache_bust
 RUN cd vllm && \
     git checkout ${VLLM_REF} && \
     echo "\n\n========================================" && \