[clang] [clang][Modules] Respect -fnocxx-modules as a driver flag (PR #150349)

[Cyndy Ishida via cfe-commits]

cyndyishida wrote:

This PR would also resolve: https://github.com/llvm/llvm-project/issues/57432 , but I'm not sure if its still relevant for the affected client code 

https://github.com/llvm/llvm-project/pull/150349