[clang] [AArch64][Driver] Enable host supported features with march=native. (PR #177128)

[David Green via cfe-commits]

davemgreen wrote:

I believe that -march=native should behave the same as -mcpu=native, enabling all the tuning features too. It is then a drop in replacement for the x86 equivalent option. Would it be possible to change it to work that way? So that we set the cpu to native when the arch is native.

https://github.com/llvm/llvm-project/pull/177128