Interpreting nix-shell -vvvvv output


I am trying to fix an issue that has bothered me for a while, namely when I try to build luakit with the new lua infrastructure, the build creates 2 luajit environments, one empty and one with the correct dependency (luafilesystem). I am trying to track down why via running:
nix-build -A luakit . --check -vvvvv 1>test.txt 2>&1 from this branch

For instance should I be worried to see the line evaluating file '/home/teto/nixpkgs2/pkgs/development/interpreters/lua-5/5.2.nix' just after the luajit invocation ? I can’t see the link between the 2 messages. It seems weird to me:

evaluating file '/home/teto/nixpkgs2/pkgs/top-level/lua-packages.nix'
evaluating file '/home/teto/nixpkgs2/pkgs/development/lua-modules/generated-packages.nix'
evaluating file '/home/teto/nixpkgs2/pkgs/development/lua-modules/overrides.nix'
evaluating file '/home/teto/nixpkgs2/pkgs/development/interpreters/lua-5/build-lua-package.nix'
trace: luajit-2.1.0-beta3
evaluating file '/home/teto/nixpkgs2/pkgs/development/interpreters/lua-5/5.2.nix'
processing attribute 'LuaCPathSearchPaths'
processing attribute 'LuaPathSearchPaths'

(full output at 2,2 MB)