suitable clang stdenv

pkgs/stdenv/default.nix

@@ -33,6 +33,12 @@ rec {
     pkgs = stdenvNativePkgs;
   };
 
+  stdenvDarwin = import ./darwin {
+    inherit config;
+    stdenv = stdenvNative;
+    pkgs = stdenvNativePkgs;
+  };
+
 
   # Linux standard environment.
   stdenvLinux = (import ./linux { inherit system allPackages platform config;}).stdenvLinux;
@@ -47,7 +53,7 @@ rec {
     if system == "armv7l-linux" then stdenvLinux else
     if system == "mips64el-linux" then stdenvLinux else
     if system == "powerpc-linux" then /* stdenvLinux */ stdenvNative else
-    if system == "x86_64-darwin" then stdenvNix else
+    if system == "x86_64-darwin" then stdenvDarwin else
     if system == "x86_64-solaris" then stdenvNix else
     stdenvNative;
 }