[clang] [C++20] [Modules] Convert '-fexperimental-modules-reduced-bmi' to '-fmodules-reduced-bmi' (PR #114382)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

I'd like to land this in the next week if no objection comes in.

https://github.com/llvm/llvm-project/pull/114382