[llvm] Use TargetABI to assign default-target features in getDefaultSubtargetFeatures (PR #100833)

[Craig Topper via llvm-commits]

topperc wrote:

The ABI might be in the TargetMachine via `Options.MCOptions.getABIName()`.

RISCVTargetMachine::getSubtargetImpl checks that the module ABI matches it.

https://github.com/llvm/llvm-project/pull/100833