Object: add a comment explaining a divergence

Add a note about the reason for the divergence from the specification
for ld64.  Addresses post-commit review comments from Davide.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294594 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed