COFF: Fix use-after-free in /msvclto implementation.
COFF: Fix use-after-free in /msvclto implementation.

The Archive object owns the memory buffers of any thin archive members, so we
need to make sure the object is still in scope when we access archive members.

Differential Revision: https://reviews.llvm.org/D31066

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@298033 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld