[flang-commits] [flang] [flang] [mlir] Avoid clobbering mlir-tblgen target by defining dummy imported targets (PR #150987)

[via flang-commits]

Acture wrote:

> I suppose the same issue will arise if someone tries to build just `mlir` (without `flang`) with a Nix sandbox, so it seems it is worth a more general fix for `mlir`. I must admit, I still do not understand what happens in your build process, so I hope a more general `mlir` fix will attract reviewers who understand this change.

That’s the odd part — building mlir with Nix works fine on my end. The problem only shows up when building flang without a dummy target, where it fails with:
`ninja: error: 'include/flang/Optimizer/Dialect/CUF/Attributes/MLIR-TBLGen', needed by 'include/flang/Optimizer/Dialect/CUF/Attributes/CUFEnumAttr.h.inc', ...`
It seems the breakage is specific to flang’s build setup rather than mlir in isolation, which I suspect is due to a missing tablegen definition, resulting in no generated output.

https://github.com/llvm/llvm-project/pull/150987