reewide: Purge all uses stdenv.system and top-level system

It is deprecated and will be removed after 18.09.

pkgs/applications/networking/insync/default.nix

@@ -4,13 +4,13 @@ stdenv.mkDerivation rec {
   name = "insync-${version}";
   version = "1.4.5.37069";
   src =
-    if stdenv.system == "x86_64-linux" then
+    if stdenv.hostPlatform.system == "x86_64-linux" then
       fetchurl {
         url = "http://s.insynchq.com/builds/insync-portable_${version}_amd64.tar.bz2";
         sha256 = "0mkqgpq4isngkj20c0ygmxf4cj975d446svhwvl3cqdrjkjm1ybd";
       }
     else
-      throw "${name} is not supported on ${stdenv.system}";
+      throw "${name} is not supported on ${stdenv.hostPlatform.system}";
 
   buildInputs = [ makeWrapper ];