Fix test breakage from r221386

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221389 91177308-0d34-0410-b5e6-96231b3b80d8
Add accessor to get 'visibility' part of st_other field

This new `getVisibility()` function will also be used in the LLD code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221392 91177308-0d34-0410-b5e6-96231b3b80d8