Lua 5.2 causes tests to fail

[jagapiou]

e.g. https://github.com/deepmind/meltingpot/actions/runs/1999939516

Until this is fixed better to use Lua 5.1 rather than Lua 5.2. This may have an impact on building Melting Pot on Apple M1 chips, see #13.

[jagapiou]

Specifically the error is:

self = <dmlab2d.Environment object at 0x15f0bfa90>
    def reset(self):
      """See base class."""
      self._reset_next_step = False
>     self._env.start(self._next_episode, seed=self._rng.randint(0, 2**31))
E     ValueError: Failed to start: 
E     ERROR: ./meltingpot/lua/modules/component_library.lua:261: Error: Must call Transform:start(...) before Transform:getPiece().
E     stack trace-back:
E     ERROR: [C]: in function 'assert'
E     ERROR: @./meltingpot/lua/modules/component_library.lua:261:
E     ERROR: @/Users/runner/work/meltingpot/meltingpot/meltingpot/lua/levels/commons_harvest/components.lua:143: in function 'start'
E     ERROR: @./meltingpot/lua/modules/game_object.lua:423: in function 'func'
E     ERROR: @./meltingpot/lua/modules/game_object.lua:160: in function '_doOnAllComponents'
E     ERROR: @./meltingpot/lua/modules/game_object.lua:420: in function 'start'
E     ERROR: @./meltingpot/lua/modules/base_simulation.lua:465: in function 'start'
E     ERROR: @./meltingpot/lua/modules/api_factory.lua:100: