Portable Ruby 4.0.1

[p-linnane]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) with your changes locally?

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This will need some fixes. Let's see what CI says.

[MikeMcQuaid]

Let's see what CI says.

it says: 🔴 😭

Thanks for getting this started. 👍🏻 once 💚

[p-linnane]

irb issue should be fixed by Homebrew/homebrew-core#264587.

[p-linnane]

Still need to fix INCFLAGS, but wanted to fix conflicts.