[Bugfix] fix custom op GmmSwigluQuantWeightNzTensorList (#4593)

### 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

---------

Signed-off-by: QianChenxi <chenxi.qian.cq@outlook.com>

csrc/build_aclnn.sh

@@ -31,4 +31,3 @@ bash build.sh -n $CUSTOM_OPS -c $SOC_ARG
 
 # install custom ops to vllm_ascend/_cann_ops_custom
 ./output/CANN-custom_ops*.run --install-path=$ROOT_DIR/vllm_ascend/_cann_ops_custom
-source $ROOT_DIR/vllm_ascend/_cann_ops_custom/vendors/customize/bin/set_env.bash