CMake modernization #1119

Job	Run time
Emscripten	1m 23s
macOS (-DRMLUI_SAMPLES_BACKEND=auto)	58s
macOS (-DRMLUI_SAMPLES_BACKEND=GLFW_GL2)	54s
Windows (-DRMLUI_SAMPLES_BACKEND=auto -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF)	4m 27s
Windows (-DRMLUI_SAMPLES_BACKEND=Win32_VK -DRMLUI_VK_DEBUG=ON)	6m 56s
Windows (-DRMLUI_SAMPLES_BACKEND=SDL_VK -DRMLUI_BUILD_LUA_BINDINGS_FOR_LUAJIT=ON)	4m 22s
Linux (clang, clang++, -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF -DRMLUI_SAMPLES_BACKEND=GLFW_GL2)	35s
Linux (clang, clang++, -DRMLUI_SAMPLES_BACKEND=SDL_VK)	51s
Linux (-DRMLUI_BUILD_TESTING=ON -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF, true)	31s
Linux (-DRMLUI_FONT_INTERFACE="" -DRMLUI_ENABLE_LOTTIE_PLUGIN=ON -DRMLUI_SAMPLES_BACKEND=X11_GL2)	26s
Linux (-DRMLUI_DISABLE_RTTI_AND_EXCEPTIONS=ON -DRMLUI_SAMPLES_BACKEND=SDL_GL2)	25s
Linux (-DRMLUI_NO_THIRDPARTY_CONTAINERS=ON -DRMLUI_SAMPLES_BACKEND=SFML_GL2)	36s
Linux (-DRMLUI_SAMPLES_BACKEND=SDL_VK -DRMLUI_VK_DEBUG=ON -DRMLUI_ENABLE_PRECOMPILED_HEADERS=OFF ...	51s
	23m 15s

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