ubsan: integer-overflow: depend on BROKEN to keep this out of CI

ubsan: integer-overflow: depend on BROKEN to keep this out of CI

Depending on !COMPILE_TEST isn't sufficient to keep this feature out of
CI because we can't stop it from being included in randconfig builds.
This feature is still highly experimental, and is developed in lock-step
with Clang's Overflow Behavior Types[1]. Depend on BROKEN to keep it
from being enabled by anyone not expecting it.

Link: https://discourse.llvm.org/t/rfc-v2-clang-introduce-overflowbehaviortypes-for-wrapping-and-non-wrapping-arithmetic/86507
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202505281024.f42beaa7-lkp@intel.com
Fixes: 557f8c582a9b ("ubsan: Reintroduce signed overflow sanitizer")
Acked-by: Eric Biggers <ebiggers@kernel.org>
Link: https://lore.kernel.org/r/20250528182616.work.296-kees@kernel.org
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kees Cook <kees@kernel.org>