Do not try to open traceme on special PIDs

src/platform/redox/ptrace.rs

@@ -52,6 +52,8 @@ pub fn init_state() -> &'static State {
     }
 }
 pub fn is_traceme(pid: pid_t) -> bool {
+    // Skip special PIDs (<=0)
+    if pid <= 0 { return false; }
     File::open(
         &CString::new(format!("chan:ptrace-relibc/{}/traceme", pid)).unwrap(),
         fcntl::O_PATH,