issue 20415 - add test case

[ghost]

Issue closed as WORKSFORME because it was fixed at some point.
Add the original test case in case of.

[dlang-bot]

Thanks for your pull request and interest in making D better, @tungstenheart! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
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• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✗	20415	regression	ice in dwarfeh and when optimizations are enabled

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#12285"