Move the addition of the dwo_id as late as possible after everything
has been finalized except for sizes and offsets. Update test accordingly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188199 91177308-0d34-0410-b5e6-96231b3b80d8
Fix warning about unused member.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188200 91177308-0d34-0410-b5e6-96231b3b80d8