[llvm] [SystemZ] Fix compile time regression in adjustInliningThreshold(). (PR #137527)

[Ulrich Weigand via llvm-commits]

https://github.com/uweigand approved this pull request.

LGTM as well, thanks!   This should also go into LLVM 20 to fix the regression.

https://github.com/llvm/llvm-project/pull/137527