feat(cmake): add ENABLE_LOTTIE_PLUGIN

Signed-off-by: Longtao Zhang <DragonBillow@outlook.com>

CMakeLists.txt

@@ -163,6 +163,7 @@ endif()
 
 option(BUILD_SAMPLES "Build samples" OFF)
 option(RMLUI_FREETYPE_EXTERNAL "Use external FreeType instead of by find_package" OFF)
+option(RMLUI_RLOTTIE_EXTERNAL "Use external RLOTTIE" OFF)
 
 set(SAMPLES_BACKEND "auto" CACHE STRING "Backend platform and renderer used for the samples.")
 set_property(CACHE SAMPLES_BACKEND PROPERTY STRINGS auto Win32_GL2 Win32_VK X11_GL2 SDL_GL2 SDL_GL3 SDL_VK SDL_SDLrenderer SFML_GL2 GLFW_GL2 GLFW_GL3 GLFW_VK)
@@ -369,7 +370,12 @@ if(BUILD_LUA_BINDINGS)
 endif()
 
 # rlottie
-if( ENABLE_LOTTIE_PLUGIN )
+if( ENABLE_LOTTIE_PLUGIN AND RMLUI_RLOTTIE_EXTERNAL )
+	message(STATUS "use external rlottie")
+	list(APPEND CORE_LINK_LIBS rlottie::rlottie)
+	list(APPEND CORE_INCLUDE_DIRS rlottie::rlottie)
+endif()
+if( ENABLE_LOTTIE_PLUGIN AND NOT RMLUI_RLOTTIE_EXTERNAL)
 	# Try to find the rlottie library.
 	if(NOT DEFINED rlottie_DIR)
 		set(rlottie_DIR $ENV{RLOTTIE_DIR})