[CI] fix docker image build by specifying merge-base commit id when downloading pre-compiled wheels (#29930)

Signed-off-by: Shengqi Chen <harry-chen@outlook.com>

docker/Dockerfile

@@ -196,6 +196,7 @@ ARG SCCACHE_S3_NO_CREDENTIALS=0
 
 # Flag to control whether to use pre-built vLLM wheels
 ARG VLLM_USE_PRECOMPILED=""
+ARG VLLM_MERGE_BASE_COMMIT=""
 ARG VLLM_MAIN_CUDA_VERSION=""
 
 # Use dummy version for csrc-build wheel (only .so files are extracted, version doesn't matter)
@@ -216,6 +217,7 @@ RUN --mount=type=cache,target=/root/.cache/uv \
         && export SCCACHE_IDLE_TIMEOUT=0 \
         && export CMAKE_BUILD_TYPE=Release \
         && export VLLM_USE_PRECOMPILED="${VLLM_USE_PRECOMPILED}" \
+        && export VLLM_PRECOMPILED_WHEEL_COMMIT="${VLLM_MERGE_BASE_COMMIT}" \
         && export VLLM_MAIN_CUDA_VERSION="${VLLM_MAIN_CUDA_VERSION}" \
         && export VLLM_DOCKER_BUILD_CONTEXT=1 \
         && sccache --show-stats \
@@ -233,6 +235,7 @@ RUN --mount=type=cache,target=/root/.cache/ccache \
         rm -rf .deps && \
         mkdir -p .deps && \
         export VLLM_USE_PRECOMPILED="${VLLM_USE_PRECOMPILED}" && \
+        export VLLM_PRECOMPILED_WHEEL_COMMIT="${VLLM_MERGE_BASE_COMMIT}" && \
         export VLLM_DOCKER_BUILD_CONTEXT=1 && \
         python3 setup.py bdist_wheel --dist-dir=dist --py-limited-api=cp38; \
     fi