libaom: disable runtime cpu detection on darwin (#112685)
libaom: disable runtime cpu detection on darwin (#112685)

CPU detection is only enabled for PPC and ARM. It's also not implemented
on Darwin, so no reason to keep it enabled there. This helps #105026.
NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs