[dsymutil] Correctly handle DW_TAG_label

This patch contains logic for handling DW_TAG_label that's present in
darwin's dsymutil implementation, but not yet upstream.

Differential revision: https://reviews.llvm.org/D43438

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325600 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed