Summary:
If the linker is invoked with `--chroot /foo` and `/bar/baz.o`, it
tries to read the file from `/foo/bar/baz.o`. This feature is useful
when you are dealing with files created by the --reproduce option.
Reviewers: grimar
Subscribers: llvm-commits, emaste
Differential Revision: https://reviews.llvm.org/D35517
llvm-svn: 308646