[llvm] [z/OS] Add z/OS archive reading support (PR #187110)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

That's quite a python script! I'm not sure I'm going to be able to fully review it, because of my lack of familiarity with the format. It would be worth another reviewer taking a look.

I've concentrated this review round on the tests primarily. It's possible some of the cases I've highlighted are covered, but I couldn't tell which, so figured it would be better to flag them.

https://github.com/llvm/llvm-project/pull/187110