[llvm] [SystemZ] Implement ctor/dtor emission via @@SQINIT and .xtor sections (PR #171476)

[Ulrich Weigand via llvm-commits]

https://github.com/uweigand commented:

Looks good to me now, but have a look at the inline comment and the check failures.  Thanks!

https://github.com/llvm/llvm-project/pull/171476