Remove windows check for cmake to build Fused kernels (#91909)
# Summary
Add support for fused attention kernels (FlashAttention and memory-efficient attention) on Windows. Previously we could not do this because the fixes required c++17 to do this but we have since update the PyTorch standard.
This PR:
- Changes invocations of unsigned long to the fixed width integer type
- Adds in the #define FP16_SWITCH(COND, ...) which has been added to the flash_attention main branch
- Changes the some macros used within mem-efficient attention code in order to work around the VA_ARG discrepancy between clang/gcc and msvc. An alternative would be setting the global flag Zc:preprocessor
- Selectively applies /Zc:lambda to only the mem-efficient sources since applying this globally caused quantization files to not compile
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91909
Approved by: https://github.com/cpuhrsch
