Compile error due to halo2curves `asm` feature can only be enabled on x86_64 arch.

Meet error, when build with `1.89.0-nightly`


```
error: failed to run custom build command for `halo2curves v0.9.0`

Caused by:
  process didn't exit successfully: `Spartan2/target/release/build/halo2curves-d78c81e30337b63f/build-script-build` (exit status: 1)
  --- stderr
  Currently feature `asm` can only be enabled on x86_64 arch.
warning: build failed, waiting for other jobs to finish...
```