Due to a BTRFS issue in kernel 6.12 (and backported in Ubuntu to 6.8)
there's a warning triggered by some tests, and it then causes a panic.

The BTRFS issue has a patch but it is not available in any distro yet,
so disable panic_on_warn until it reaches Arch and Ubuntu Noble. Bugs
have been filed.

(cherry picked from commit 930d65cc)
(cherry picked from commit 72ef5ac2)