Auto merge of #115964 - bjorn3:cgu_reuse_tracker_global_state, r=cjgillot

Remove cgu_reuse_tracker from Session

This removes a bit of global mutable state.

It will now miss post-lto cgu reuse when ThinLTO determines that a cgu doesn't get changed, but there weren't any tests for this anyway and a test for it would be fragile to the exact implementation of ThinLTO in LLVM.

compiler/rustc_codegen_ssa/src/lib.rs

@@ -46,6 +46,7 @@ use std::collections::BTreeSet;
 use std::io;
 use std::path::{Path, PathBuf};
 
+pub mod assert_module_sources;
 pub mod back;
 pub mod base;
 pub mod codegen_attrs;