Bug Error compiling with flash attn

[super-fun-surf]

this was working fine until recent commit

cargo run --example stable-diffusion-3 --features cuda,cudnn,flash-attn -- --prompt "donkey" --which 3.5-large --use-flash-attn

gives error

error[E0384]: cannot assign twice to immutable variable `builder`
  --> candle-flash-attn/build.rs:93:13
   |
76 |     let builder = bindgen_cuda::Builder::default()
   |         ------- first assignment to `builder`
...
93 |             builder = builder.arg("-D_USE_MATH_DEFINES");
   |             ^^^^^^^ cannot assign twice to immutable variable
   |
help: consider making this binding mutable
   |
76 |     let mut builder = bindgen_cuda::Builder::default()
   |         +++

For more information about this error, try `rustc --explain E0384`.
error: could not compile `candle-flash-attn` (build script) due to 1 previous error

[LaurentMazare]

Sorry about that, fix in #2754

[super-fun-surf]

Works great. Thanks!