[CI] Fix python install ci error

[yewentao256]

Purpose

FIx https://buildkite.com/vllm/ci/builds/41328#019adb74-3db0-49ce-84fd-34859b6d7ff3

I can't reproduce this locally, let's run CI and see if it could be solved.

[chatgpt-codex-connector]

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[gemini-code-assist]

Code Review

This pull request introduces changes to setup.py to address a CI failure during Python installation with precompiled binaries. The precompiled_build_ext class is updated to set the build output directory to the project root, which should help in locating the precompiled artifacts correctly. Additionally, the vllm.triton_kernels extension is now excluded from the build process when VLLM_USE_PRECOMPILED is active, preventing a potentially redundant or failing compilation step. The proposed changes are logical and seem to be a reasonable approach to resolving the CI issue. The code is clear and adheres to standard practices. I have not identified any high or critical severity issues in this pull request.

[DarkLight1337]

We have decided to revert #29690 to fix the issue. Closing as superseded by #29838 which is a patched version of the reverted PR.