OSRM can't be compiled with GCC 10

[akashihi]

Outdated Sol2 library prevents OSRM compilation with gcc 10:

osrm-backend/third_party/sol2/sol2/sol.hpp:6919:40: error: call of overloaded ‘push<const char32_t*>(lua_State*&, const char32_t [2], const char32_t*)’ is ambiguous
 6919 |     return stack::push<const char32_t*>(L, str, str + sz);
In file included from osrm-backend/include/extractor/scripting_environment_lua.hpp:15,
                 from osrm-backend/src/extractor/scripting_environment_lua.cpp:1:
osrm-backend/third_party/sol2/sol2/sol.hpp:4600:14: note: candidate: ‘int sol::stack::push(lua_State*, T&&, Args&& ...) [with T = const char32_t*; Args = {const char32_t*}; lua_State = lua_State]’
 4600 |   inline int push(lua_State* L, T&& t, Args&&... args) {
osrm-backend/third_party/sol2/sol2/sol.hpp:4606:14: note: candidate: ‘int sol::stack::push(lua_State*, Arg&&, Args&& ...) [with T = const char32_t*; Arg = const char32_t (&)[2]; Args = {const char32_t*}; <template-parameter-1-4> = void; lua_State = lua_State]’
 4606 |   inline int push(lua_State* L, Arg&& arg, Args&&... args) {

Sol2 needs to be updated to at least 2.19.4

[systemed]

Now that #5887 has landed (inter alia), can we close this?

[mloskot]

@akashihi I'm closing this assuming it's been fixed now.