lib,mount: Fix type annotations and module visibility

- Make tempmount module public in bootc-mount crate so it can be
  imported by bootc-lib
- Add type annotation for booted_bls to help type inference
- Add return type annotation for closure in atomic_replace_with
- Fix rustix features in bootc-mount Cargo.toml

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Author: ericcurtin

crates/lib/src/bootc_composefs/boot.rs

@@ -730,7 +730,7 @@ pub(crate) fn setup_composefs_bls_boot(
     let (config_path, booted_bls) = if is_upgrade {
         let boot_dir = Dir::open_ambient_dir(&entry_paths.config_path, ambient_authority())?;
 
-        let mut booted_bls = get_booted_bls(&boot_dir)?;
+        let mut booted_bls: BLSConfig = get_booted_bls(&boot_dir)?;
         booted_bls.sort_key = Some(secondary_sort_key(&os_id));
 
         let staged_path = loader_path.join(STAGED_BOOT_LOADER_ENTRIES);

crates/lib/src/install.rs

@@ -2046,7 +2046,7 @@ fn copy_regular_file<ObjectID: FsVerityHashValue>(
             // For external files, stream from the object store
             let mut reader = std::fs::File::from(repo.open_object(id)?);
             dest_dir
-                .atomic_replace_with(dest_path, |writer| {
+                .atomic_replace_with(dest_path, |writer| -> Result<(), std::io::Error> {
                     std::io::copy(&mut reader, writer)?;
                     Ok(())
                 })

crates/mount/src/lib.rs

@@ -6,5 +6,5 @@
 mod mount;
 pub use mount::*;
 
-mod tempmount;
+pub mod tempmount;
 pub use tempmount::*;