[llvm] [llvm-dwp] Add missing llvm-dwp tool in lit config tool substitution (PR #81217)

[David Blaikie via llvm-commits]

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

Sure, I guess - I forget why we need these substitutions, but seems like a reasonable thing to add to the list.

https://github.com/llvm/llvm-project/pull/81217