[Chapel Merge] Fix spurious extern-record-union error

Branch: refs/heads/main
Revision: 93308f8
Author: mppf
Log Message:

Merge pull request #17991 from mppf/fix-extern-union-record-error

Fix spurious extern-record-union error

Follow-up to PR #17752.

Resolves a spurious error message with

test/runtime/configMatters/interop/unordered-atomics.chpl

Reviewed by @lydia-duncan - thanks!