https://issues.dlang.org/show_bug.cgi?id=21160

          Issue ID: 21160
           Summary: DWARF: DW_AT_main_subprogram should be emitted for
                    _Dmain
           Product: D
           Version: D2
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: lucien.perregaux@gmail.com

So that the debugger knows that it is the starting function instead of the
main() in entrypoint.d.

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