MC: correct DWARF line info for PE/COFF

DWARF address ranges contain a reference to the debug_info section.  This offset
is an absolute relocation except on non-PE/COFF targets where it is section
relative.  We would emit this incorrectly, and trying to map the debug info from
the address would fail.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217317 91177308-0d34-0410-b5e6-96231b3b80d8