### What this PR does / why we need it?
In the past time, we used a hybrid architecture cross-compilation
approach for image building. This method had a problem:
cross-compilation performance was very poor, leading to extremely long
build times(abort 4h) and even a probability of failure(see
https://github.com/vllm-project/vllm-ascend/actions/runs/20152861650/job/57849208186).
Therefore, I recommend using a separate architecture build followed by
manifest merging, which significantly reduces image build time(20min).
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
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Signed-off-by: wangli <wangli858794774@gmail.com>
