darwin.apple_sdk_11_0: code cleanup

pkgs/os-specific/darwin/apple-sdk-11.0/default.nix

@@ -82,25 +82,25 @@ let
   callPackage = newScope (packages // pkgs.darwin // { inherit MacOSX-SDK; });
 
   packages = stdenvs // {
-    inherit (callPackage ./apple_sdk.nix {}) frameworks libs;
+    inherit (callPackage ./apple_sdk.nix { }) frameworks libs;
 
     # TODO: this is nice to be private. is it worth the callPackage above?
     # Probably, I don't think that callPackage costs much at all.
     inherit MacOSX-SDK CLTools_Executables;
 
-    Libsystem = callPackage ./libSystem.nix {};
+    Libsystem = callPackage ./libSystem.nix { };
     LibsystemCross = pkgs.darwin.Libsystem;
-    libcharset = callPackage ./libcharset.nix {};
-    libunwind = callPackage ./libunwind.nix {};
-    libnetwork = callPackage ./libnetwork.nix {};
-    libpm = callPackage ./libpm.nix {};
+    libcharset = callPackage ./libcharset.nix { };
+    libunwind = callPackage ./libunwind.nix { };
+    libnetwork = callPackage ./libnetwork.nix { };
+    libpm = callPackage ./libpm.nix { };
     # Avoid introducing a new objc4 if stdenv already has one, to prevent
     # conflicting LLVM modules.
-    objc4 = if stdenv ? objc4 then stdenv.objc4 else callPackage ./libobjc.nix {};
+    objc4 = stdenv.objc4 or (callPackage ./libobjc.nix { });
 
     # questionable aliases
     configd = pkgs.darwin.apple_sdk.frameworks.SystemConfiguration;
-    IOKit = pkgs.darwin.apple_sdk.frameworks.IOKit;
+    inherit (pkgs.darwin.apple_sdk.frameworks) IOKit;
 
     xcodebuild = pkgs.xcbuild.override {
       inherit (pkgs.darwin.apple_sdk_11_0) stdenv;
@@ -115,7 +115,16 @@ let
     callPackage = newScope (lib.optionalAttrs stdenv.isDarwin (stdenvs // rec {
       inherit (pkgs.darwin.apple_sdk_11_0) xcodebuild rustPlatform;
       darwin = pkgs.darwin.overrideScope (_: prev: {
-        inherit (prev.darwin.apple_sdk_11_0) Libsystem LibsystemCross libcharset libunwind objc4 configd IOKit Security;
+        inherit (prev.darwin.apple_sdk_11_0)
+          IOKit
+          Libsystem
+          LibsystemCross
+          Security
+          configd
+          libcharset
+          libunwind
+          objc4
+          ;
         apple_sdk = prev.darwin.apple_sdk_11_0;
         CF = prev.darwin.apple_sdk_11_0.CoreFoundation;
       });