[LEGACY] [CI]: stty output not always there (EL8 only?)

### Description

Sometimes, calling `stty` does not seem to output anything.
Witnessed on EL8.

Can stty fail silently?
Why would it return nothing?

### Steps to reproduce the issue

1.
2.
3.

### Describe the results you received and expected

```
=== RUN TestExecTTY/stty_with_-t
=== PAUSE TestExecTTY/stty_with_-t
=== CONT TestExecTTY/stty_with_-t
container_exec_linux_test.go:110:

+============================================================================================================+
| 🚀 | "TestExecTTY/stty_with_-t": starting test! |
+============================================================================================================+
| temp | /tmp/TestExecTTYstty_with_-t24[778](https://github.com/containerd/nerdctl/actions/runs/14520021992/job/40738434866#step:10:779)13565/001 |
+============================================================================================================+
| config | { |
| | "Namespace": "nerdctl-test", |
| | "PrivateMode": "" |
| | } |
+============================================================================================================+
| data | { |
| | "container_name": "testexectty-3d80652a" |
| | } |
+============================================================================================================+

container_exec_linux_test.go:110:

+------------------------------------------------------------------------------------------------------------+
| ➡️ | ⚙️ /usr/local/bin/nerdctl exec -t testexectty-3d80652a stty |
+------------------------------------------------------------------------------------------------------------+
| 🌱 | XDG_SESSION_TYPE=tty |
| | HOME=/home/rootless |
| | XDG_SESSION_CLASS=user |
| | XDG_SESSION_ID=4 |
| | XDG_RUNTIME_DIR=/run/user/1001 |
| | PATH=/usr/local/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin |
| | :/bin:/usr/games:/usr/local/games:/snap/bin |
| | DOCKER_CONFIG=/tmp/TestExecTTYstty_with_-t247[781](https://github.com/containerd/nerdctl/actions/runs/14520021992/job/40738434866#step:10:782)3565/001 |
| | NERDCTL_TOML=/tmp/TestExecTTYstty_with_-t2477813565/001/nerdctl.toml |
+------------------------------------------------------------------------------------------------------------+
| ⏰ | <1s (limit: 3m0s) |
+------------------------------------------------------------------------------------------------------------+
| 📁 | /tmp/TestExecTTYstty_with_-t2477813565/001 |
+------------------------------------------------------------------------------------------------------------+

container_exec_linux_test.go:110:

<<<<<<<<<<<<<<<<<<<<
🖊️ Inspecting output (contains)
👀 testing: ``
❌ FAILED! ~= `speed 38400 baud`
>>>>>>>>>>>>>>>>>>>>

--- FAIL: TestExecTTY/stty_with_-t (0.14s)
```

### What version of nerdctl are you using?

main

### Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

### Host information

_No response_