[clang] [Clang] Remove AArch64TargetInfo::setArchFeatures (PR #146107)

[David Green via cfe-commits]

davemgreen wrote:

The best kind of patch.

> When compiling with -march=armv9-a+nosve we found that Clang still defines the __ARM_FEATURE_SVE2 macro

Could we add a test for this, in case it comes up again in the future? Negative features have not worked super well in the past and could do with extra test coverage.

https://github.com/llvm/llvm-project/pull/146107