generates the dwarf Compile Unit DIE and a dwarf subprogram DIE for each
non-temporary label.
The next part will be to get the clang driver to enable this when assembling
a .s file. rdar://9275556
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146262 91177308-0d34-0410-b5e6-96231b3b80d8