Unable to build with the latest nightly

When building with the latest nightly, I got the following error:
```
error: expected one of `!` or `::`, found keyword `mod`
   --> src/lib.rs:347:7
    |
347 | crate mod llvm {
    |       ^^^ expected one of `!` or `::`

error: could not compile `packed_simd_2` due to previous error
```