difftest: fix tests on windows

Author: Firestar99

tests/difftests/runner/src/testcase.rs

@@ -164,13 +164,13 @@ mod tests {
             .test_binaries
             .sort_by(|a, b| a.relative_path.cmp(&b.relative_path));
         assert_eq!(
-            test_case.test_binaries[0].relative_path.to_string_lossy(),
-            "test_case/pkg1"
+            test_case.test_binaries[0].relative_path,
+            Path::new("test_case/pkg1")
         );
         assert_eq!(test_case.test_binaries[0].absolute_path, pkg1_dir);
         assert_eq!(
-            test_case.test_binaries[1].relative_path.to_string_lossy(),
-            "test_case/pkg2"
+            test_case.test_binaries[1].relative_path,
+            Path::new("test_case/pkg2")
         );
         assert_eq!(test_case.test_binaries[1].absolute_path, pkg2_dir);
     }