Workaround for filesystems that round timestamps to 1-second precision

Fixes rust-lang#2874

src/cargo/core/compiler/fingerprint/mod.rs

@@ -1888,7 +1888,19 @@ where
         // if equal, files were changed just after a previous build finished.
         // Unfortunately this became problematic when (in #6484) cargo switch to more accurately
         // measuring the start time of builds.
-        if path_mtime <= reference_mtime {
+        //
+        // Additionally, the build can span different volumes, some which support high-precision
+        // file timestamps and some that don't (e.g. mounted Docker volumes). This can make
+        // one of the timestamps lose the nanosecond part and appear up to a second in the past.
+        let truncated_precision = path_mtime.nanoseconds() == 0;
+
+        let fresh = if truncated_precision {
+            path_mtime.unix_seconds() <= reference_mtime.unix_seconds()
+        } else {
+            path_mtime <= reference_mtime
+        };
+
+        if fresh {
             continue;
         }