[clang] [llvm] [mlir] [MLIR][CMake] Model transitive generated header dependencies (PR #222170)

[Erich Keane via llvm-commits]

erichkeane wrote:

FWIW: this doesn't seem to have an impact on the ClangIR build times best I can tell.  Not sure if is expected to, or if this is a prerequisite for others.  But as an FYI! 

https://github.com/llvm/llvm-project/pull/222170