buildLuarocksPackage: rework fixup phase

[teto]

I was working on lua tests, enabling nlua and I started overriding postFixup, which removed the default phase for build-luarocks-package so instead let's make it a proper phase.

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[cole-h]

You'll want to rebase on the latest master -- there was an issue that broke ofborg's ability to evaluate Nixpkgs that has since been resolved. Sorry for the inconvenience!

[teto]

@cole-h ty. since this targets staging, I will wait for the next master merge in staging.

[cole-h]

It looks like this actually targets master. Was that a mistake? 😄

[teto]

it is ! ty I almost triggered an apocalypse rebuild (I hope I would noticed the 5000 rebuilds once eval had passed xD)

[vcunat]

This commit broke lua*.tests.checkSetupHook (and knot-resolver); mentioned also in #300905 (comment)

[teto]

hum I checked in pkgs/stdenv/generic/setup.sh and the standard phase does a lot of stuff, while the rest of the diff seems harmless, overriding the default one may have broken. I am on holiday, feel free to revert I will push something better later.