[PATCH] nplt: Fix MADV_GUARD_INSTALL logic for thread without guard page (BZ 33356)

[Florian Weimer]

* Adhemerval Zanella:

> The main issue is that setup_stack_prot fails to account for cases where
> the cached thread stack lacks a guard page, which can cause madvise to
> fail. Update the logic to also handle whether MADV_GUARD_INSTALL is
> supported when resizing the guard page.
>
> Checked on x86_64-linux-gnu with 6.8.0 and 6.15 kernels.

Typo in commit subject, should be nptl.

Florian