[clang] [OpenMP] clang/Driver/Options.td - fix typo in fopenmp-force-usm HelpText (PR #93599)

[Thibault Monnier via cfe-commits]

Thibault-Monnier wrote:

Unfortunately, that’s a problem LLVM faces. There are over 6k open pull requests, with only about 50-100 merged per day, of which old one often get forgotten.

https://github.com/llvm/llvm-project/pull/93599