min-list-garbage: check all store paths against file

this is step 1 of min-collect-garbage, no point implementing
deletion ourselves when rm -r exists

(arguably no point in implementing any of it, but this is the bit we
can't do efficiently in bourne shell - it means we're reading the
store-paths list once instead of grepping it afresh for every entry in
/nix/store/)

pkgs/min-copy-closure/default.nix

@@ -8,9 +8,13 @@
   buildInputs = [ ];
   propagatedBuildInputs = [ cpio openssh nix ];
   src = ./.;
+  makeFlags = [ "min-list-garbage" ];
   installPhase = ''
     mkdir -p $out/bin
-    cp min-copy-closure.sh $out/bin/min-copy-closure
-    cp liminix-rebuild.sh $out/bin/liminix-rebuild
+    for i in min-copy-closure liminix-rebuild; do
+      echo $i
+      cp ''${i}.sh $out/bin/$i
+    done
+    cp min-list-garbage $out/bin
   '';
 }