[lld][inputgraph] Fix build failure on Darwin/Windows

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192083 91177308-0d34-0410-b5e6-96231b3b80d8
[lld][Darwin] Fix unused field warning.

This field would eventually be used.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192084 91177308-0d34-0410-b5e6-96231b3b80d8