[llvm] [mlir] [Flang][OpenMP][OpenMPIRBuilder] Implement module scope declare target use rewrite mechanism (PR #212920)

[Sergio Afonso via llvm-commits]

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

Thank you Andrew, I only have non-blocking comments so LGTM! No need for another look by me after addressing the nits.

https://github.com/llvm/llvm-project/pull/212920