Re-unique_ptrify LoadedObjectInfo::clone after it was reverted due to some other...

Re-unique_ptrify LoadedObjectInfo::clone after it was reverted due to some other changes that broke on GCC around the same time

Apparently this functionality isn't used in-tree (or I would go & make
the explicit unique_ptr constructions into implicit constructions to
make them more self documenting now that clone doesn't return a raw
owning pointer anymore) but only by the Julia frontend. This isn't
ideal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239091 91177308-0d34-0410-b5e6-96231b3b80d8