Ignore llvm.* globals.

It is not clear if llvm.global_ctors should or should not be in llvm.metadata,
but in practice it is not and we need to ignore it for LTO.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212351 91177308-0d34-0410-b5e6-96231b3b80d8