fix autodiff build

Author: ZuseZ4

compiler/rustc_builtin_macros/src/autodiff.rs

@@ -3,7 +3,7 @@
 //! configs (autodiff enabled or disabled), so we have to add cfg's to each import.
 //! FIXME(ZuseZ4): Remove this once we have a smarter linter.
 
-#[cfg(llvm_enzyme)]
+//#[cfg(llvm_enzyme)]
 mod llvm_enzyme {
     use std::str::FromStr;
     use std::string::String;
@@ -242,6 +242,7 @@ mod llvm_enzyme {
             defaultness: ast::Defaultness::Final,
             sig: d_sig,
             generics: Generics::default(),
+            contract: None,
             body: Some(d_body),
         });
         let mut rustc_ad_attr =