handbrake: fix Darwin build (#89674)
handbrake: fix Darwin build (#89674)

- Omit the numactl dependency under Darwin.
- Prevent the configure script from checking for xcodebuild. This check
  always failed (because xcodebuild isn't available in the build
  context) but xcodebuild isn't actually needed for the build, which
  uses --disable-xcode.
- Use the Nix-provided libxml2 under Darwin like we already do under
  Linux.
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