https://issues.dlang.org/show_bug.cgi?id=23713

          Issue ID: 23713
           Summary: compilable/testcstuff1.c:206:1: error: static
                    assertion failed: sizeof(u'a') == 4
           Product: D
           Version: D2
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: ibuclaw@gdcproject.org

When compiling the test with `gcc -std=c11 -fsyntax-only`

compilable/testcstuff1.c:206:1: error: static assertion failed: "ok"
  206 | _Static_assert(sizeof(u'a') == 4, "ok");
      | ^~~~~~~~~~~~~~

Test case:
```
_Static_assert(sizeof(u'a') == 4, "ok");
```

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