added compile flag for gcc9 (was somehow an error on my system)

CMakeLists.txt

 cmake_minimum_required(VERSION 3.10)
 MESSAGE (STATUS "cmake version: ${CMAKE_VERSION}")
+
 # If OS is Ubuntu 20 we nned to change some things
 execute_process(COMMAND lsb_release -cs
     OUTPUT_VARIABLE RELEASE_CODENAME
@@ -95,6 +96,10 @@ if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 8.0)
     add_compile_options(-Wno-error=sign-compare)
 endif()
 
+if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 9.0)
+    add_compile_options(-Wno-error=deprecated-copy)
+endif()
+
 #######################################################################################
 #options
 OPTION (Simox_USE_RBDL_LIB "Use RBDL" ON)