Update to ruby-4.0.0

[larskanis]

No description provided.

[flavorjones]

This is not going to work until dockerhub images are updated, and setup-ruby is updated.

I would advise just updating the ruby version in the container as a first step.

[flavorjones]

See related https://bugs.ruby-lang.org/issues/21804

[larskanis]

You're right!

[flavorjones]

I've opened an alternative that just updates the version in the container image: #182

[larskanis]

Closing this in favor of #182 .

[larskanis]

Release versions of extensions are not compatible with pre-release ruby. They raise

/opt/hostedtoolcache/Ruby/4.0.0-preview3/x64/lib/ruby/gems/4.0.0+1/gems/rcd_test-1.0.0-x86_64-linux/lib/rcd_test.rb:3:in 'Kernel#require':
/opt/hostedtoolcache/Ruby/4.0.0-preview3/x64/lib/ruby/gems/4.0.0+1/gems/rcd_test-1.0.0-x86_64-linux/lib/rcd_test/4.0/rcd_test_ext.so:
undefined symbol: ruby_abi_version - ruby_abi_version (LoadError)

Like here: https://github.com/rake-compiler/rake-compiler-dock/actions/runs/20507193772/job/58924268124#step:6:31

New PR: #183