CMake modernization #1190

Job	Run time
Emscripten	6m 58s
macOS (-DRMLUI_SAMPLES_BACKEND=GLFW_GL2)	5m 12s
Linux (clang, clang++, -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF -DRMLUI_SAMPLES_BACKEND=GLFW_GL2)	1m 48s
Linux (clang, clang++, -DRMLUI_SAMPLES_BACKEND=SDL_VK -DSDL_LIBRARY=SDL2 -DSDL_INCLUDE_DIR=/usr/i...	1m 44s
Linux (-DRMLUI_BUILD_TESTING=ON -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF, true)	2m 16s
Linux (-DRMLUI_ENABLE_LOTTIE_PLUGIN=ON -DRMLUI_SAMPLES_BACKEND=X11_GL2)	1m 54s
Linux (-DRMLUI_DISABLE_RTTI_AND_EXCEPTIONS=ON -DRMLUI_SAMPLES_BACKEND=SDL_GL2 -DSDL_LIBRARY=SDL2 ...	1m 50s
Linux (-DRMLUI_NO_THIRDPARTY_CONTAINERS=ON -DRMLUI_SAMPLES_BACKEND=SFML_GL2)	1m 53s
Linux (-DRMLUI_SAMPLES_BACKEND=SDL_VK -DRMLUI_VK_DEBUG=ON -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF ...	2m 3s
Windows (-DRMLUI_SAMPLES_BACKEND=Win32_VK -DRMLUI_VK_DEBUG=ON -DVulkan_LIBRARY="C:\VulkanSDK\1.3....	9m 49s
Windows (-DRMLUI_SAMPLES_BACKEND=SDL_VK -DRMLUI_BUILD_LUA_BINDINGS_FOR_LUAJIT=ON -DVulkan_LIBRARY...	11m 10s
	46m 37s

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