Fix 21792 - Enum using itself as base type crashes dmd

[MoonlightSentinel]

Run semantic on the base type to resolve all missing properties and to detect invalid forward references.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	21792	normal	Enum using itself as base type crashes dmd

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#12347"