Log Message:
lang/elixit: Update to 1.6.2.

1. Enhancements

Mix
- [mix compile.erlang] Teach Mix erlang compiler alternative spelling
  for -behavior declaration
- [mix format] Support the :subdirectories configuration that points
  to other directories with their own .formatter.exs file. This is
  useful in umbrella applications. mix new --umbrella has also been
  changed to use this new configuration by default
- [mix format] Include the current environment for missing dependency
  errors

2. Bug fixes

Elixir
- [Code.Formatter] Ensure -> does not exceed line length
- [DynamicSupervisor] Properly tag error reports generated by dynamic
  supervisors so they can be properly translated by Logger
- [DynamicSupervisor] Consider extra arguments during child restart
- [Kernel] Ensure arguments given to a guard defined with defguard are
  evaluated in the correct order
- [Module] Do not remove docs for previous function declaration when
  @impl true is used
- [Supervisor] Ensure use Supervisor properly adds the @behaviour
  Supervisor annotation

Mix
- [Mix.Shell] Bring back Mix.Shell.cmd/2 - this arity was defined via
  a default argument that was accidentally removed