stdenv.mkDerivation: simplify overrideAttrs with extends and toOverlay

pkgs/stdenv/generic/make-derivation.nix

@@ -67,26 +67,8 @@ let
       #              ^^^^
 
       overrideAttrs = f0:
-        let
-          f = self: super:
-            # Convert f0 to an overlay. Legacy is:
-            #   overrideAttrs (super: {})
-            # We want to introduce self. We follow the convention of overlays:
-            #   overrideAttrs (self: super: {})
-            # Which means the first parameter can be either self or super.
-            # This is surprising, but far better than the confusion that would
-            # arise from flipping an overlay's parameters in some cases.
-            let x = f0 super;
-            in
-              if builtins.isFunction x
-              then
-                # Can't reuse `x`, because `self` comes first.
-                # Looks inefficient, but `f0 super` was a cheap thunk.
-                f0 self super
-              else x;
-        in
-          makeDerivationExtensible
-            (self: let super = rattrs self; in super // (if builtins.isFunction f0 || f0?__functor then f self super else f0));
+        makeDerivationExtensible
+          (lib.extends (lib.toExtension f0) rattrs);
 
       finalPackage =
         mkDerivationSimple overrideAttrs args;