`callcc` is a private global function, so `respond_to?(:callcc)` is always false and these tests have been skipped since 5621d794a2. Builds that disable `callcc` still skip them, because `respond_to?` returns false for not-implemented methods even with `include_all`.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
(cherry picked from commit 3a3a921ac6c02b4269a2c6d4c6cb30d06fa6892e)