README.md for macOS build steps results in compilation error

[henrik-web3]

Describe the bug
Following build steps in main README.md for macOS resulted in build error.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://github.com/nomacs/nomacs#build-nomacs-macos
2. Follow the steps to the letter
3. Encounter a build error
4. See error log last in this ticket.

Expected behavior
Build should pass

Desktop (please complete the following information):
Apple M2 Pro 16 GB

• OS: macOS Ventura
• Version: Version 13.3 (22E252)

Additional context
First time user trying to compile the software, without it succeeding.

Build Log:

CMake Deprecation Warning at CMakeLists.txt:3 (cmake_minimum_required):
  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.


-- The C compiler identification is AppleClang 14.0.3.14030022
-- The CXX compiler identification is AppleClang 14.0.3.14030022
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- QuaZip disabled - it's not supported on OSX
-- Could NOT find WrapVulkanHeaders (missing: Vulkan_INCLUDE_DIR) 
-- QuaZip disabled - it's not supported for Qt6
-- A release build (non-debug). Debugging outputs are silently ignored.
-- exiv2 version by pkg-config: 0.28.2
-- exiv2 contains exiv2.hpp, using it
-- 
-- APPLE: some hacks with OpenCV libraries linking will be performed (only limited set of libs will be used)
-- APPLE:    originals: opencv_core;opencv_imgproc
-- APPLE:          new: opencv_core;opencv_imgproc
-- 
-- /Users/henrik/Code/nomacs/ImageLounge/src/themes/Dark-Theme.css added...
-- /Users/henrik/Code/nomacs/ImageLounge/src/themes/Light-Theme.css added...
-- /Users/henrik/Code/nomacs/ImageLounge/src/themes/System.css added...
-- I failed to locate plugins in: /Users/henrik/Code/nomacs/ImageLounge/plugins
CMake Warning at CMakeLists.txt:255 (message):
  plugins directory not found, not building plugins.  You have to check out
  the nomacs-plugins git to the 'plugins' folder if you want to build them


-- 
-- ----------------------------------------------------------------------------------
--  nomacs - Image Lounge 3.17  <https://nomacs.org>
--  Qt version: 6.6.2
--  nomacs will be compiled with OPENCV support .................. YES
--  nomacs will be compiled with LIBRAW support .................. YES
--  nomacs will be compiled with extended TIFF support ........... YES
--  nomacs will be compiled with plugin support .................. NO
--  nomacs will be compiled with HEIF support .................... NO
--  nomacs will be compiled with Translations .................... YES
--  nomacs will be compiled with QuaZip support .................. NO
-- ----------------------------------------------------------------------------------
-- Configuring done (1.4s)
-- Generating done (0.0s)
-- Build files have been written to: /Users/henrik/Code/nomacs/build
[  0%] Built target nomacsCore_autogen_timestamp_deps
[  1%] Automatic MOC for target nomacsCore
[  1%] Built target nomacsCore_autogen
[  2%] Building CXX object CMakeFiles/nomacsCore.dir/nomacsCore_autogen/mocs_compilation.cpp.o
[  3%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkBaseWidgets.cpp.o
[  4%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkBatch.cpp.o
[  5%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkCentralWidget.cpp.o
[  6%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkConnection.cpp.o
[  8%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkControlWidget.cpp.o
[  9%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkDialog.cpp.o
[ 10%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkDockWidgets.cpp.o
[ 11%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkLogWidget.cpp.o
[ 12%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkManipulatorWidgets.cpp.o
[ 13%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkMenu.cpp.o
[ 14%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkMetaDataWidgets.cpp.o
[ 16%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkNetwork.cpp.o
[ 17%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkNoMacs.cpp.o
[ 18%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkPong.cpp.o
[ 19%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkPreferenceWidgets.cpp.o
[ 20%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkQuickAccess.cpp.o
[ 21%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkSettingsWidget.cpp.o
[ 22%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkThumbsWidgets.cpp.o
[ 24%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkToolbars.cpp.o
[ 25%] Building CXX object CMakeFiles/nomacsCore.dir/src/DkGui/DkViewPort.cpp.o
/Users/henrik/Code/nomacs/ImageLounge/src/DkGui/DkViewPort.cpp:1982:30: error: no member named 'WA_MacNoShadow' in namespace 'Qt'
    parent->setAttribute(Qt::WA_MacNoShadow);
                         ~~~~^
1 error generated.
make[2]: *** [CMakeFiles/nomacsCore.dir/src/DkGui/DkViewPort.cpp.o] Error 1
make[1]: *** [CMakeFiles/nomacsCore.dir/all] Error 2
make: *** [all] Error 2