[Object] Deduplicate long archive member names

Summary:
Import libraries as created by llvm-dlltool always use the same archive
member name for every object file (namely, the DLL library name). Ensure
that long names are not repeatedly stored in the string table.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D55860

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349637 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed