trunk/29c701469ca2df4605194613ca70f3bba41e4abe: Enable FA build for SDPA on Windows+CUDA (#186343)

发生了什么

Summary Description Enable building the FlashAttention backend for scaled_dot_product_attention on Windows + CUDA (MSVC). Today, the flag is hard-disabled on MSVC, so every Windows CUDA build ships without the flash SDPA backend and silently falls back to slower, memory-heavy backends. With this PR, the FlashAttention kernels now build cleanly under modern MSVC, which restores the fast path. Why this matters On Wind…

摘要按规则整理自下方来源原文

来源