[flang] [llvm] [mlir] [flang][MLIR][OpenMP] make reduction by-ref toggled per variable (PR #92244)

[David Truby via llvm-commits]

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

LGTM but wait for approval from Kiran

https://github.com/llvm/llvm-project/pull/92244