[clang] [Driver] Restrict Ofast deprecation help message to Clang (PR #101682)

[Fangrui Song via cfe-commits]

MaskRay wrote:

Thanks for the clarification!
Cc some flang developers to confirm this is the direction as https://discourse.llvm.org/t/rfc-deprecate-ofast-in-flang/80243 doesn't have lots of recorded discussion: @banach-space @clementval  @klausler 

https://github.com/llvm/llvm-project/pull/101682