[clang] [llvm] [AArch64][Driver] Fix behavior of +nofeat modifier on -mcpu (PR #203458)

[Tomas Matheson via cfe-commits]

https://github.com/tommat01 commented:

Thanks for working on this. It would be good to state/show explicitly what the GCC behaviour in this area is.

https://github.com/llvm/llvm-project/pull/203458