[llvm] [llvm-ar] --help: fix unquoted angle bracket (PR #101364)

[James Henderson via llvm-commits]

https://github.com/jh7370 requested changes to this pull request.

So I don't think the `<` is actually spurious! llvm-ar only supports reading MRI scripts from stdin, not from a file specified directly on the command-line. In this case, `<` is intended to represent the "read stdin from file" indicator. I think this would be clearer if there was a space between the `<` and `mri-script`.

https://github.com/llvm/llvm-project/pull/101364