squashfsTools: make Darwin patch apply to 4.4
squashfsTools: make Darwin patch apply to 4.4

I took the patch, and applied it on top of the previous squashfs-tools
commit that we packaged. It applied cleanly. Then I rebased that on top
of master, and resolved the conflicts. I'm not sure I resolved them
correctly though, I don't have access to Darwin. Somebody needs to
review this.

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