The generated yarnNix file doesn't need to be part of the mkDerivation.
And doing so prevents other platforms from reproducibly instantiating
it. With this change you can e.g. do
darwinPkgs.yarn2nix.mkYarnPackage {
# ...
yarnNix = pkgs.yarn2nix.mkYarnNix {
yarnLock = ./yarn.lock;
};
}
Which is a darwin derivation, but can still be instantiated reproducibly on Linux.
