Add more metadata to rustc_fingerprint

src/cargo/util/rustc.rs

@@ -6,6 +6,7 @@ use std::sync::Mutex;
 
 use anyhow::Context as _;
 use cargo_util::{paths, ProcessBuilder, ProcessError};
+use filetime::FileTime;
 use serde::{Deserialize, Serialize};
 use tracing::{debug, info, warn};
 
@@ -329,7 +330,13 @@ fn rustc_fingerprint(
         let path = paths::resolve_executable(path)?;
         path.hash(hasher);
 
-        paths::mtime(&path)?.hash(hasher);
+        let meta = paths::metadata(&path)?;
+        meta.len().hash(hasher);
+
+        // Often created and modified are the same, but not all filesystems support the former,
+        // and distro reproducible builds may clamp the latter, so we try to use both.
+        FileTime::from_creation_time(&meta).hash(hasher);
+        FileTime::from_last_modification_time(&meta).hash(hasher);
         Ok(())
     };