Add godotcpp 3.4 (#764)

packages/g/godotcpp/xmake.lua

@@ -6,6 +6,7 @@ package("godotcpp")
     set_urls("https://github.com/godotengine/godot-cpp.git")
     add_versions("3.2", "77d41fa179e40560f1e264ed483638bf51713779")
     add_versions("3.3", "dfee6f0ca41863eacdd47bd3c1c4afa46cc97fa4")
+    add_versions("3.4", "4efceefe138b2494e3c691e1dead1c60efb621b1")
 
     add_deps("scons")