nixpkgs/pkgs/development/libraries/gobject-introspection/setup-hook.sh

make_gobject_introspection_find_gir_files() {

    # required for .typelib files, eg mypaint git version
    if [ -d "$1/lib/girepository-1.0" ]; then
      addToSearchPath GI_TYPELIB_PATH $1/lib/girepository-1.0
    fi

    # XDG_DATA_DIRS: required for .gir files?
    if [ -d "$1/share" ]; then
      addToSearchPath XDG_DATA_DIRS $1/share
    fi
}

envHooks+=(make_gobject_introspection_find_gir_files)

_multioutMoveGlibGir() {
  moveToOutput share/gir-1.0 "${!outputDev}"
}

preFixupHooks+=(_multioutMoveGlibGir)