Print threads backtrace on SIGINFO/SIGPWR

[sobrinho]

Description

Debugging stuck builds is always tricky and this will add a thread backtrace dump to STDERR when the process is signaled with SIGINFO (macOS) or SIGPWR (linux).

On macOS you can use CTRL+T to signal the running process. Linux you can use kill -PWR pid.

I have a PR open against RSpec as well here.

This is a common pattern used by Sidekiq and Puma that I'm aware of but possibly other projects as well.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds new behaviour)

Please add an entry to the relevant section of CHANGELOG.md as part of this pull request.

Checklist:

Your PR is ready for review once the following checklist is
complete. You can also add some checks if you want to.

• Tests have been added for any changes to behaviour of the code
• New and existing tests are passing locally and on CI
• bundle exec rubocop reports no offenses
• RDoc comments have been updated
• CHANGELOG.md has been updated

[luke-hill]

Ignore any failing tests in CI for the CCK

[luke-hill]

This has CI failures related to this code. I'm currently knee-deep in investigating / fixing up other areas of the main codebase so won't be able to dive into this much in the next 1-2 weeks

[sobrinho]

@luke-hill fixed