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

[via cfe-commits]

yamash-fj wrote:

@tommat01 
To preserve the existing behaivor, I changed the initialization order; set base arch defaults after enabling CPU-default features.

> One consequence of this change is that a feature implied by both the CPU and the base architecture is no longer emitted on the cc1 command line. I believe this is only removing redundant +<feat> entries and does not affect the generated IR. However it requires updating a number of existing tests. I have updated some of them, although I have not finished updating all affected tests yet.

As a result, the existing tests no longer need to be updated, and I have reverted those test changes.

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