### What this PR does / why we need it?
1. Fixes the environment path used to locate custom op shared libraries.
2. Uses empty tensor initialization for op outputs instead of
zero-initialization for better efficiency.
- vLLM version: v0.11.2
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.2
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Signed-off-by: QianChenxi <chenxi.qian.cq@outlook.com>
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