CMake snippet to add to CMakeLists.txt to make some target use `int main()` while building to the GUI ("windows") subsystem.

WindowsGuiSubsystemWithMain.cmake

# No console window when targetting windows
if(WIN32)
	function(handle_gnu_style_compiler)
		# Supposedly the flag -mwindows would automatically make the executable use GUI subsystem
		# But, when subsystem is set to GUI, linker will only search WinMain and wWinMain but not the standard main (it seems like)
		# so creating GUI executable fails and the linker silently reverts to the default, CUI subsystem
		target_link_options(${TARGET_NAME} PRIVATE -Wl,-subsystem:windows)
		target_link_options(${TARGET_NAME} PRIVATE -Wl,-entry:mainCRTStartup)
	endfunction()
	function(handle_msvc_style_compiler)
		target_link_options(${TARGET_NAME} PRIVATE /SUBSYSTEM:windows /ENTRY:mainCRTStartup)
	endfunction()
	if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
		# GCC (MinGW)
		handle_gnu_style_compiler()
	elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
		if(CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC")
			# MSVC-style argument clang (clang-cl.exe)
			handle_msvc_style_compiler()
		elseif(CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
			# GNU-style argument clang (clang.exe and clang++.exe)
			handle_gnu_style_compiler()
		endif()
	elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
		handle_msvc_style_compiler()
	endif()
endif()