[llvm] [Support] Show '[subcommand]' in the help for less than 3 subcommands (PR #74557)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM. Strange that the original patch (https://github.com/llvm/llvm-project/commit/79f3333d3f04c26cde06a663dca7b79e1ac86345) used `> 2` for "at least 1". I wonder if some refactoring later caused the issue?

https://github.com/llvm/llvm-project/pull/74557