Add fine-grained Elixir version requirement

1.4 is accepted in general
1.10 is required to build OTP releases
1.11 is required to run 'make relive'
lower than 1.11.4 requires Erlang lower than 24 to build releases

mix.exs

@@ -5,7 +5,7 @@ defmodule Ejabberd.MixProject do
     [app: :ejabberd,
      version: version(),
      description: description(),
-     elixir: "~> 1.4",
+     elixir: elixir_required_version(),
      elixirc_paths: ["lib"],
      compile_path: ".",
      compilers: [:asn1] ++ Mix.compilers,
@@ -184,6 +184,35 @@ defmodule Ejabberd.MixProject do
     end
   end
 
+  defp elixir_required_version do
+    case {System.get_env("RELIVE", "false"),
+          MapSet.member?(MapSet.new(System.argv()), "release")}
+      do
+      {"true", _} ->
+        case Version.match?(System.version(), "~> 1.11") do
+          false ->
+            IO.puts("ERROR: To use 'make relive', Elixir 1.11.0 or higher is required.")
+          _ -> :ok
+        end
+        "~> 1.11"
+      {_, true} ->
+        case Version.match?(System.version(), "~> 1.10") do
+          false ->
+            IO.puts("ERROR: To build releases, Elixir 1.10.0 or higher is required.")
+          _ -> :ok
+        end
+        case Version.match?(System.version(), "< 1.11.4")
+          and :erlang.system_info(:otp_release) > '23' do
+          true ->
+            IO.puts("ERROR: To build releases with Elixir lower than 1.11.4, Erlang/OTP lower than 24 is required.")
+          _ -> :ok
+        end
+        "~> 1.10"
+      _ ->
+        "~> 1.4"
+    end
+  end
+
   defp releases do
     maybe_tar = case Mix.env() do
       :prod -> [:tar]
@@ -228,7 +257,7 @@ defmodule Ejabberd.MixProject do
     end
 
     # Mix/Elixir lower than 1.11.0 use config/releases.exs instead of runtime.exs
-    case Version.match?(System.version, ">= 1.11.0") do
+    case Version.match?(System.version, "~> 1.11") do
       true ->
         :ok
       false ->