[clang] [llvm] [mlir] [openmp] [OpenMP][offload] Cross-team reductions with variable number of teams (PR #195102)

[Robert Imschweiler via cfe-commits]

ro-i wrote:

Extracted a stripped-down version of https://github.com/ro-i/xteam-test and opened https://github.com/llvm/llvm-project/pull/195940

https://github.com/llvm/llvm-project/pull/195102