[clang] [mlir] [mlir,CIR][CMake] Declare the generated headers each library includes (PR #221829)

[Mehdi Amini via cfe-commits]

joker-eph wrote:

> My agent believes these are fixed.

You missed my point: these were just *examples* that show how fragile this is and why the pattern is in place.
There are many additions to `*IncGen` dependencies in this patch that just don't seem maintainable: listing all the transitive generated header dependencies on every target is not a good design.

We need:

- a CMake way to manage this dependencies (similar to Bazel?)
- a CI deterministically failing if the build is incorrectly configured (`ninja -t missingdeps` was giving us false positive in the past somehow)



https://github.com/llvm/llvm-project/pull/221829