Switch from AtomicU64 to Mutex.

Not all platforms support AtomicU64, so this swaps the usage with
Mutex. The difference in performance should be imperceptible.

crates/cargo-util/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cargo-util"
-version = "0.2.8"
+version = "0.2.9"
 rust-version.workspace = true
 edition.workspace = true
 license.workspace = true

crates/cargo-util/src/du.rs

@@ -4,7 +4,6 @@ use anyhow::{Context, Result};
 use ignore::overrides::OverrideBuilder;
 use ignore::{WalkBuilder, WalkState};
 use std::path::Path;
-use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex};
 
 /// Determines the disk usage of all files in the given directory.
@@ -40,7 +39,7 @@ fn du_inner(path: &Path, patterns: &[&str]) -> Result<u64> {
         .git_ignore(false)
         .git_exclude(false);
     let walker = builder.build_parallel();
-    let total = Arc::new(AtomicU64::new(0));
+    let total = Arc::new(Mutex::new(0u64));
     // A slot used to indicate there was an error while walking.
     //
     // It is possible that more than one error happens (such as in different
@@ -52,7 +51,8 @@ fn du_inner(path: &Path, patterns: &[&str]) -> Result<u64> {
                 Ok(entry) => match entry.metadata() {
                     Ok(meta) => {
                         if meta.is_file() {
-                            total.fetch_add(meta.len(), Ordering::SeqCst);
+                            let mut lock = total.lock().unwrap();
+                            *lock += meta.len();
                         }
                     }
                     Err(e) => {
@@ -73,5 +73,6 @@ fn du_inner(path: &Path, patterns: &[&str]) -> Result<u64> {
         return Err(e);
     }
 
-    Ok(total.load(Ordering::SeqCst))
+    let total = *total.lock().unwrap();
+    Ok(total)
 }