emqx4.3/apps/emqx/rebar.config.script

Bcrypt = {bcrypt, {git, "https://github.com/emqx/erlang-bcrypt.git", {branch, "0.6.0"}}},
AddBcrypt = fun(C) ->
    {deps, Deps0} = lists:keyfind(deps, 1, C),
    Deps = [Bcrypt | Deps0],
    lists:keystore(deps, 1, C, {deps, Deps})
end,

case os:type() of
    {win32, _} -> CONFIG;
    _ -> AddBcrypt(CONFIG)
end.