I think as a result of b36ab48 and/or 1e3e36a, the nix develop environment no longer functions:

$ ./Meta/ladybird.sh run ladybird
~/Software/ladybird/Toolchain/Tarballs ~/Software/ladybird/Toolchain
Preset CMake variables:

  CMAKE_BUILD_TYPE="RelWithDebInfo"
  CMAKE_TOOLCHAIN_FILE="/home/quentin/Software/ladybird/Toolchain/Tarballs/vcpkg/scripts/buildsystems/vcpkg.cmake"
  SERENITY_CACHE_DIR="/home/quentin/Software/ladybird/Build/caches"
  VCPKG_INSTALL_OPTIONS="--no-print-usage"
  VCPKG_OVERLAY_TRIPLETS="/home/quentin/Software/ladybird/Meta/CMake/vcpkg/release-triplets"

Preset environment variables:

  LADYBIRD_SOURCE_DIR="/home/quentin/Software/ladybird"
  VCPKG_BINARY_SOURCES="clear;files,/home/quentin/Software/ladybird/Toolchain/Build/vcpkg-binary-cache,readwrite"
  VCPKG_ROOT="/home/quentin/Software/ladybird/Toolchain/Tarballs/vcpkg"

-- Running vcpkg install
Could not start dynamically linked executable: /home/quentin/Software/ladybird/Toolchain/Tarballs/vcpkg/vcpkg
NixOS cannot run dynamically linked executables intended for generic
linux environments out of the box. For more information, see:
https://nix.dev/permalink/stub-ld
-- Running vcpkg install - failed
CMake Error at Toolchain/Tarballs/vcpkg/scripts/buildsystems/vcpkg.cmake:899 (message):
  vcpkg install failed.  See logs for more information:
  /home/quentin/Software/ladybird/Build/ladybird/vcpkg-manifest-install.log
Call Stack (most recent call first):
  /nix/store/vnhl4zdy7igx9gd3q1d548vwzz15a9ma-cmake-3.27.7/share/cmake-3.27/Modules/CMakeDetermineSystem.cmake:148 (include)
  CMakeLists.txt:3 (project)


CMake Error: CMake was unable to find a build program corresponding to "Ninja".  CMAKE_MAKE_PROGRAM is not set.  You probably need to select a different build tool.
-- Configuring incomplete, errors occurred!

This appears to be because BuildVcpkg.sh is trying to download and run a pre-compiled executable, which doesn't work on NixOS. It needs to either use the vcpkg from nix (not currently part of the dependencies in Ladybird/default.nix), build vcpkg from source instead of installing a binary, or just use the Nix-provided versions of libraries instead of the vcpkg-provided ones.