A Qt-consuming target with all its sources skipping usage of precompile headers breaks AUTOMOC

Project can be built with either Qt 5.15 or Qt 6.

cmake_minimum_required(VERSION 3.16)
project(issue LANGUAGES CXX)

find_package(QT NAMES Qt5 Qt6 REQUIRED COMPONENTS Core)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)
set(CMAKE_AUTOMOC ON)

file(GENERATE OUTPUT "widget.h" CONTENT "
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
class Widget : public QWidget {
    Q_OBJECT
public:
    Widget(QWidget *parent = nullptr);

};
#endif
")
file(GENERATE OUTPUT "widget.cpp" CONTENT "
#include \"widget.h\"
Widget::Widget(QWidget *parent) : QWidget(parent) {}
")

add_library(mylib STATIC ${CMAKE_BINARY_DIR}/widget.cpp ${CMAKE_BINARY_DIR}/widget.h)
target_link_libraries(mylib PRIVATE Qt::Widgets)

set_source_files_properties(${CMAKE_BINARY_DIR}/widget.cpp ${CMAKE_BINARY_DIR}/widget.h
    PROPERTIES SKIP_PRECOMPILE_HEADERS ON)

target_precompile_headers(mylib PRIVATE [["QWidget"]])

$ mkdir build && cd build && cmake -DCMAKE_PREFIX_PATH=/path/to/Qt .. && ninja

Build output

makeobj[0]: Entering directory `~/Dev/automoc_no_dep_on_pch/build'
ninja: error: 'CMakeFiles/mylib.dir/cmake_pch.hxx.pch', needed by 'CMakeFiles/mylib.dir/mylib_autogen/mocs_compilation.cpp.o', missing and no known rule to make it
makeobj[0]: Leaving directory `~/Dev/automoc_no_dep_on_pch/build'

Enabling precompiled headers on the target, but excluding all the target sources from using the precompiled header file seemingly causes the generation of the .pch file not to happen.

And yet AUTOMOC relies on the .pch file to exist implicitly, which sounds like a bug. Either it shouldn't depend on the .pch file, or it should ensure it is generated.