Revert r353424 "[llvm-ar][libObject] Fix relative paths when nesting thin archives."

This broke the Chromium build on Windows, see

> Summary:
> When adding one thin archive to another, we currently chop off the relative path to the flattened members. For instance, when adding `foo/child.a` (which contains `x.txt`) to `parent.a`, whe
> lattening it we should add it as `foo/x.txt` (which exists) instead of `x.txt` (which does not exist).
> As a note, this also undoes the `IsNew` parameter of handling relative paths in r288280. The unit test there still passes.
> This was reported as part of testing the kernel build with llvm-ar: (see the second point).
> Reviewers: mstorsjo, pcc, ruiu, davide, david2050
> Subscribers: hiraditya, llvm-commits
> Tags: #llvm
> Differential Revision:

This reverts commit bf990ab5aab03aa0aac53c9ef47ef264307804ed.

git-svn-id: 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed