buildLuarocksPackage: ability to self reference extraConfig (#288253)

makes overrideAttrs for lua packages even more powerful.
As a consequence, it simplifies the implementation of buildNeovimPlugin.

pkgs/applications/editors/neovim/build-neovim-plugin.nix

@@ -19,14 +19,14 @@ in
     let
       originalLuaDrv = lua.pkgs.${luaAttr};
 
-      luaDrv = (lua.pkgs.luaLib.overrideLuarocks originalLuaDrv (drv: {
+      luaDrv = originalLuaDrv.overrideAttrs (oa: {
+        version = attrs.version or oa.version;
+        rockspecVersion = oa.rockspecVersion;
+
         extraConfig = ''
           -- to create a flat hierarchy
           lua_modules_path = "lua"
         '';
-        })).overrideAttrs (drv: {
-        version = attrs.version or drv.version;
-        rockspecVersion = drv.rockspecVersion;
       });
 
       finalDrv = toVimPlugin (luaDrv.overrideAttrs(oa: attrs // {

pkgs/development/interpreters/lua-5/build-luarocks-package.nix

@@ -92,7 +92,7 @@ let
     luarocks
   ];
 
-  inherit doCheck extraVariables rockspecFilename knownRockspec externalDeps nativeCheckInputs;
+  inherit doCheck extraConfig extraVariables rockspecFilename knownRockspec externalDeps nativeCheckInputs;
 
   buildInputs = let
     # example externalDeps': [ { name = "CRYPTO"; dep = pkgs.openssl; } ]
@@ -131,7 +131,7 @@ let
     in
       ''
       ${generatedConfig}
-      ${extraConfig}
+      ${self.extraConfig}
       '';
 
   configurePhase = ''