Fix an [-Werror,-Winconsistent-missing-override] error.


git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221312 91177308-0d34-0410-b5e6-96231b3b80d8
Use LLVMLIBS here since these are produced by the
llvm build and not supposed to be resident on
the system.


git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221314 91177308-0d34-0410-b5e6-96231b3b80d8