Deny `dead_code` and `unused_variables` at crate level

framework/aster-frame/src/lib.rs

@@ -16,8 +16,6 @@
 #![feature(ptr_sub_ptr)]
 #![feature(strict_provenance)]
 #![feature(pointer_is_aligned)]
-#![allow(dead_code)]
-#![allow(unused_variables)]
 // The `generic_const_exprs` feature is incomplete however required for the page table
 // const generic implementation. We are using this feature in a conservative manner.
 #![allow(incomplete_features)]

kernel/aster-nix/src/lib.rs

@@ -3,9 +3,7 @@
 //! The std library of Asterinas.
 #![no_std]
 #![deny(unsafe_code)]
-#![allow(dead_code)]
 #![allow(incomplete_features)]
-#![allow(unused_variables)]
 #![feature(btree_cursors)]
 #![feature(btree_extract_if)]
 #![feature(const_option)]