[llvm] [mlir] Introduce LDBG_OS() macro as a variant of LDBG() (PR #157194)

[Andrzej Warzyński via llvm-commits]

https://github.com/banach-space approved this pull request.

LGTM, thanks for addressing my comments!

Please wait for @jpienaar to approve before landing.

https://github.com/llvm/llvm-project/pull/157194