Sink DwarfUnit::applyVariableAttributes into DwarfCompileUnit

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221088 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the build from the last commit

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221089 91177308-0d34-0410-b5e6-96231b3b80d8