Generate qt help file from CMake - qt

Question

I want to create a online help for my program using the qt help framework. My doc files are generated by doxygen, and I want to generate files for qt help generator from it.
My program is built with CMake, and I've added a target for generating documentation:
cmake_minimum_required (VERSION 3.21.0)
find_package(Doxygen REQUIRED dot)
set (DOXYGEN_HIDDEN_SYMBOLS "")
if (DOXYGEN_FOUND)
configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile #ONLY)
doxygen_add_docs(
myprograme-manual
${CMAKE_CURRENT_SOURCE_DIR}/en
)
endif(DOXYGEN_FOUND)
The configure_file is needed because in the configuration I use come CMake variables, like the version of my program and so on.
This is the part of the doxyfile where I create the qhp file.
GENERATE_QHP = YES
# If the QHG_LOCATION tag is specified, the QCH_FILE tag can be used to specify
# the file name of the resulting .qch file. The path specified is relative to
# the HTML output folder.
# This tag requires that the tag GENERATE_QHP is set to YES.
QCH_FILE = #DOC_OUTPUT_DIRECTORY#/manual.qch
# The QHP_NAMESPACE tag specifies the namespace to use when generating Qt Help
# Project output. For more information please see Qt Help Project / Namespace
# (see:
# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#namespace).
# The default value is: org.doxygen.Project.
# This tag requires that the tag GENERATE_QHP is set to YES.
QHP_NAMESPACE = my.program
# The QHP_VIRTUAL_FOLDER tag specifies the namespace to use when generating Qt
# Help Project output. For more information please see Qt Help Project / Virtual
# Folders (see:
# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#virtual-folders).
# The default value is: doc.
# This tag requires that the tag GENERATE_QHP is set to YES.
QHP_VIRTUAL_FOLDER = doc
# If the QHP_CUST_FILTER_NAME tag is set, it specifies the name of a custom
# filter to add. For more information please see Qt Help Project / Custom
# Filters (see:
# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-filters).
# This tag requires that the tag GENERATE_QHP is set to YES.
QHP_CUST_FILTER_NAME =
# The QHP_CUST_FILTER_ATTRS tag specifies the list of the attributes of the
# custom filter to add. For more information please see Qt Help Project / Custom
# Filters (see:
# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-filters).
# This tag requires that the tag GENERATE_QHP is set to YES.
QHP_CUST_FILTER_ATTRS =
# The QHP_SECT_FILTER_ATTRS tag specifies the list of the attributes this
# project's filter section matches. Qt Help Project / Filter Attributes (see:
# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#filter-attributes).
# This tag requires that the tag GENERATE_QHP is set to YES.
QHP_SECT_FILTER_ATTRS =
# The QHG_LOCATION tag can be used to specify the location (absolute path
# including file name) of Qt's qhelpgenerator. If non-empty doxygen will try to
# run qhelpgenerator on the generated .qhp file.
# This tag requires that the tag GENERATE_QHP is set to YES.
QHG_LOCATION =
Problem is that the file is not generated. From the comments I can see that I need to define the QHG_LOCATION parameter, that's the full path of qhelpgenerator. Since I use CMake the qt path on the computer is not fixed, and I use find_package in order to use Qt. How can I define a variable from the find_package(Qt) that allows me to define the location of the qhelpgenerator?