FHS and <package>-dev

I’m trying to reproduce this installation procedure inside an FHS environment on NixOS.

At 4:29 the list of required Ubuntu packages is shown, which includes libexpat1-dev. The most relevant-looking thing I can find in nixpkgs is expat. After adding it to the FHS environment, I can see


but I cannot find any related include directory, so it’s no great surprise that
the cmake configuration, described around 6:13 in the linked video, fails for me with

CMake Error at /nix/store/ii1fk94564x799141lqvhaf6yx0rl3ax-cmake-cursesUI-3.26.4/share/cmake-3.26/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
 Call Stack (most recent call first):
   /nix/store/ii1fk94564x799141lqvhaf6yx0rl3ax-cmake-cursesUI-3.26.4/share/cmake-3.26/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPHSA_FAILURE_MESSAGE)
   /nix/store/ii1fk94564x799141lqvhaf6yx0rl3ax-cmake-cursesUI-3.26.4/share/cmake-3.26/Modules/FindEXPAT.cmake:65 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
   cmake/Modules/G4OptionalComponents.cmake:69 (find_package)
   cmake/Modules/G4CMakeMain.cmake:59 (include)
   CMakeLists.txt:49 (include)

though it is a bit surprising that it complains not only about EXPAT_INCLUDE_DIR but also EXPAT_LIBRARY.

Is it possible to get around this problem in an FHS environment on NixOS?

Further down the line, I worry about the qt5 requirement: nixpkgs seems to have qt6 only, though there are libsForQt5.qt5ct and qt6.qt5compat; will those suffice in this context?

Expat has split outputs, so to refer to the development files add expat.dev (or lib.getDev expat) to the FHS environment.