On NixOS, if you build GHC from source using Make or hadrian and try to use it with cabal then you will be greeted with the following error:
cabal: The program 'ar' is required but it could not be found.The way to fix this problem is to run cabal in an environment with the binutils-unwrapped package available. You can then use cabal as normal.
nix-shell -p binutils-unwrapped
