Merge branch 'selftest-af_unix-misc-updates'

Kuniyuki Iwashima says:

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selftest: af_unix: Misc updates.

Patch 1 add .gitignore under tools/testing/selftests/net/af_unix/.

Patch 2 make so_peek_off.c less flaky.
====================

Link: https://patch.msgid.link/20251124212805.486235-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>