[lld-macho] Allow deduplicate-literals to be overridden

It's still uncertain but whether we want to have `deduplicate-literals` be the
default flag for LLD out of the box or not. If `deduplicate-literals` is the default
behavior, then we will need a way override it and not deduplicate. Luckily, we
have `no_deduplicate` to fill this gap. For now, I've set the default to be false
which aligns with the existing behavior. That can only always be changed after
discussions on D117250.

Reviewed By: #lld-macho, int3

Differential Revision: https://reviews.llvm.org/D117387