[llvm] Add llvm-dlltool to the toolchain list (PR #72563)

[Alexandre Ganea via llvm-commits]

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

Side note, to save on disk space, it would be really cool if these more rarely-used tools were going through llvm-driver + a stub exe (in the absence of reliable symlinks on Windows)

https://github.com/llvm/llvm-project/pull/72563