nptl: Fix MADV_GUARD_INSTALL logic for thread without guard page (BZ 33356)

nptl: Fix MADV_GUARD_INSTALL logic for thread without guard page (BZ 33356)

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.

Reviewed-by: Florian Weimer <fweimer@redhat.com>