[clang] [llvm] Add support for flag output operand "=@cc" for SystemZ. (PR #125970)

[Ulrich Weigand via llvm-commits]

https://github.com/uweigand commented:

This approach does look promising, it's much shorter, cleaner, and more general than before.  Still a number of inline comments ...

https://github.com/llvm/llvm-project/pull/125970