relibc: fix setgroups and unused ENOSYS import

src/platform/redox/mod.rs

@@ -1341,7 +1341,7 @@ impl Pal for Sys {
             Err(_) => return Err(Errno(ENOMEM)),
         };
         let mut file = match File::open(
-            CStr::from_bytes_with_nul(path_c.as_bytes_with_nul()).unwrap(),
+            CStr::borrow(&path_c),
             fcntl::O_WRONLY | fcntl::O_CLOEXEC,
         ) {
             Ok(f) => f,