fix issue 20212 - invalid debug info with enum type in library

[rainers]

reusing an old type index does not work because it might be in a different object file. Let cv_debtyp() sort out duplicates instead.

Regression is on master only (no enum type debug info emitted before). A test as in the report seems excessive, there is a test in runnable/testpdb.d that emission still works.

[dlang-bot]

Thanks for your pull request, @rainers!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20212	regression	invalid debug info with enum type in library

⚠️⚠️⚠️ Warnings ⚠️⚠️⚠️

• Regression or critical bug fixes should always target the stable branch. Learn more about rebasing to stable or the D release process.

To target stable perform these two steps:

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Testing this PR locally

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dub fetch digger
dub run digger -- build "master + dmd#10407"