This stemps from conversatin in: https://github.com/llvm/llvm-project/pull/77457#discussion_r1457889792. Right now Abbrev code for abbrev is combination of DIE TAG and other attributes. In the future it will be changed to be an index. Since DenseSet does not preserve an order, added a sort based on abbrev code. Once change to index is made, it will print out abbrevs in the order they are stored.