[BOLT][DWARF] Fix location list order

This bug crept in when CU partitioning was introduced. It manifests itself when
there are CUs that use location lists that come before CUs that are part of
thin-lto. BOLT processes CUs with cross CU references first (these are produced
by thin-lto). When we wrote out all the location lists we did it in original
order. Since DWARF4 uses offsets directly in to .debug_loc those offsets in DIEs
became wrong.

Reviewed By: Amir

Differential Revision: https://reviews.llvm.org/D157908