some overrideDerivation cleanups

These four top-level packages were the only ones that didn't have the
meta.position attribute automagically set. This commit fixes this.

pkgs/development/interpreters/luajit/default.nix

@@ -7,10 +7,8 @@ rec {
     version = "2.0.5";
     isStable = true;
     sha256 = "0yg9q4q6v028bgh85317ykc9whgxgysp76qzaqgq55y6jy11yjw7";
-  } // {
-    # 64-bit ARM isn't supported upstream
-    meta = meta // {
-      platforms = lib.filter (p: p != "aarch64-linux") meta.platforms;
+    meta = genericMeta // {
+      platforms = lib.filter (p: p != "aarch64-linux") genericMeta.platforms;
     };
   };
 
@@ -20,13 +18,12 @@ rec {
     sha256 = "1hyrhpkwjqsv54hnnx4cl8vk44h9d6c9w0fz1jfjz00w255y7lhs";
   };
 
-
-  meta = with stdenv.lib; {
+  genericMeta = with stdenv.lib; {
     description = "High-performance JIT compiler for Lua 5.1";
     homepage    = http://luajit.org;
     license     = licenses.mit;
     platforms   = platforms.linux ++ platforms.darwin;
-    maintainers = with maintainers ; [ thoughtpolice smironov vcunat andir ];
+    maintainers = with maintainers; [ thoughtpolice smironov vcunat andir ];
   };
 
   generic =
@@ -37,6 +34,7 @@ rec {
         url = "http://luajit.org/download/LuaJIT-${version}.tar.gz";
         inherit sha256;
       })
+    , meta ? genericMeta
     }:
 
     stdenv.mkDerivation rec {