nodejs: refactor derivations (#19973)

* refactor and clean up the derivation composition
* add slim variation: the slim variations configure node without npm.
Building node with npm introduces a python runtime depndency through
gyp - slim variation makes sense for building small nodejs production
images

pkgs/development/web/nodejs/v6.nix

@@ -2,24 +2,27 @@
 , pkgconfig, runCommand, which, libtool, fetchpatch
 , callPackage
 , darwin ? null
+, enableNpm ? true
 }@args:
 
 let
-  inherit (darwin.apple_sdk.frameworks) CoreServices ApplicationServices;
+  nodejs = import ./nodejs.nix args;
+  baseName = if enableNpm then "nodejs" else "nodejs-slim";
+in
+  stdenv.mkDerivation (nodejs // rec {
+    version = "6.8.0";
+    name = "${baseName}-${version}";
+    src = fetchurl {
+      url = "https://nodejs.org/download/release/v${version}/node-v${version}.tar.xz";
+      sha256 = "13arzwki13688hr1lh871y06lrk019g4hkasmg11arm8j1dcwcpq";
+    };
+
+    patches = nodejs.patches ++ [
+      (fetchpatch {
+        url = "https://github.com/nodejs/node/commit/fc164acbbb700fd50ab9c04b47fc1b2687e9c0f4.patch";
+        sha256 = "1rms3n09622xmddn013yvf5c6p3s8w8s0d2h813zs8c1l15k4k1i";
+      })
+    ];
+
+  })
 
-in import ./nodejs.nix (args // rec {
-  version = "6.8.0";
-  sha256 = "13arzwki13688hr1lh871y06lrk019g4hkasmg11arm8j1dcwcpq";
-  extraBuildInputs = stdenv.lib.optionals stdenv.isDarwin
-    [ CoreServices ApplicationServices ];
-  preBuild = stdenv.lib.optionalString stdenv.isDarwin ''
-    sed -i -e "s|tr1/type_traits|type_traits|g" \
-      -e "s|std::tr1|std|" src/util.h
-  '';
-  patches = [
-    (fetchpatch {
-      url = "https://github.com/nodejs/node/commit/fc164acbbb700fd50ab9c04b47fc1b2687e9c0f4.patch";
-      sha256 = "1rms3n09622xmddn013yvf5c6p3s8w8s0d2h813zs8c1l15k4k1i";
-    })
-  ];
-})