[llvm] [llvm-ar] Add missing right angle bracket (PR #101364)

[Fangrui Song via llvm-commits]

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

Consider editing the title (`[llvm-ar] --help: fix unquoted angle bracket`)

Just change the PR title/descritpion. The git commit message is ignored.

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