pkgs/build-support/cabal: disable the split objects feature on Darwin by default
pkgs/build-support/cabal: disable the split objects feature on Darwin by default

According to <http://hackage.haskell.org/trac/ghc/ticket/4013>, this
feature won't work with XCode versions older than 3.2.

This means that Mac users will have considerably larger binaries because
some build-time dependencies (such as HTTP) will be mis-detected as
run-time dependencies.

NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,triton/triton,NixOS/nixpkgs,NixOS/nixpkgs,triton/triton,triton/triton,triton/triton,triton/triton,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,triton/triton,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,triton/triton,NixOS/nixpkgs,SymbiFlow/nixpkgs,triton/triton,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs