7zz: add setup hook script to unpack DMG files

pkgs/tools/archivers/7zz/default.nix

···
 
   nativeBuildInputs = lib.optionals useUasm [ uasm ];
 
+  setupHook = ./setup-hook.sh;
+
   enableParallelBuilding = true;
 
   preBuild = "cd CPP/7zip/Bundles/Alone2";

pkgs/tools/archivers/7zz/setup-hook.sh

···
+unpackCmdHooks+=(_tryUnpackDmg)
+_tryUnpackDmg() {
+    if ! [[ "$curSrc" =~ \.dmg$ ]]; then return 1; fi
+    7zz x "$curSrc"
+}