Make lib imports in overlay explicit

overlay.nix

@@ -2,14 +2,14 @@ final: /* Future last stage */
 prev:  /* Previous stage */
 
 let
-  inherit (final.lib) collect isDerivation mapAttrs;
+  inherit (prev.lib) collect isDerivation mapAttrs;
 
   inherit (final) callPackage;
 
   mkDeps = name: pkgs: final.runCommand name { }
     "printf '%s\n' ${toString (collect (x: x ? outPath) pkgs)} > $out";
 
-  mkStrict = drv: if (isDerivation drv && drv ? overrideAttrs)
+  mkStrict = drv: if (isDerivation drv && drv ? overrideAttrs && !(drv ? strictDeps))
     then drv.overrideAttrs { strictDeps = true; }
     else drv;