[llvm] [TargetParser][cmake] Be Smarter about TableGen Deps (PR #144848)

[Jim Lin via llvm-commits]

https://github.com/tclin914 approved this pull request.

I've reviewed every line of this change — it looks good to me. I also tested it locally, and it works well. I hope I didn't miss anything.

https://github.com/llvm/llvm-project/pull/144848