Object: support empty UID/GID fields

Normal archives do not have empty UID/GID fields.  However, the Microsoft
Import library format is a customized archive (it just uses an alternate symbol
index format).  When the import library is constructed by lib.exe, the UID and
GID fields are left empty.  Do not abort on such an input.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274528 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed