Tweak cross-compilation of some netbsd stuff
Tweak cross-compilation of some netbsd stuff

This makes, at least, the following packages compile with musl:

* netbsd.compat
* netbsd.getent
* netbsd.fts

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