https://issues.dlang.org/show_bug.cgi?id=13742

          Issue ID: 13742
           Summary: undefined reference to __coverage
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: code@dawg.eu

This happens when building a smaller vibe.d app with -unittest and -cov.
It only happens when vibe.d was build as static library, not when it's directly
compiled with the application.
Still need to reduce a test case.

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