[CI/Build] Fix FlashInfer double build in Dockerfile

[mgoin]

Purpose

It seems there was a bad merge between #18064 and #20136 that resulted in FlashInfer being built "both ways" with both sets of TORCH_CUDA_ARCH_LIST. I'm not sure how the CUDA 11.8 build was working with this in place, but this may have resulted in some of the JIT performance weirdness observed in the last release.

Test Plan

Test Result

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[gemini-code-assist]

Summary of Changes

Hello @mgoin, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical build configuration issue in the Dockerfile related to FlashInfer. It streamlines the FlashInfer installation process by eliminating redundant build steps and ensuring that the correct CUDA architectures are targeted based on the specific CUDA version being used. This fix aims to prevent potential JIT performance anomalies observed in previous releases by resolving a 'double build' scenario.

Highlights

• FlashInfer Build Consolidation: Consolidated the FlashInfer build process within the Dockerfile, removing a redundant build step that was causing conflicting TORCH_CUDA_ARCH_LIST settings and potential performance issues.
• CUDA Architecture Targeting Logic: Refined the logic for setting the TORCH_CUDA_ARCH_LIST variable, now FI_TORCH_CUDA_ARCH_LIST, to ensure FlashInfer is built with the correct CUDA architectures (e.g., 7.5, 8.0, 8.9, 9.0a, 10.0a, 12.0) based on the specific CUDA_VERSION (11.x, 12.0-12.7, or 12.8+).
• Dockerfile Streamlining: Cleaned up the Dockerfile by removing unnecessary export TORCH_CUDA_ARCH_LIST and duplicate git clone commands, making the FlashInfer installation process more efficient and less error-prone.

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[gemini-code-assist]

Code Review

This pull request fixes a double build issue for FlashInfer in the Dockerfile by removing the redundant build process and refining the logic for CUDA architecture selection. A comment was clarified for better maintainability.

[tlrmchlsmth]

one small comment otherwise LGTM, thanks!