Record the version of Elixir used to compile ElixirLS (#264)

* Record the version of Elixir used to compile ElixirLS

* Record erlang compilation version as well

* fix typo

Author: axelson

apps/elixir_ls_utils/lib/launch.ex

@@ -1,4 +1,7 @@
 defmodule ElixirLS.Utils.Launch do
+  @compiled_elixir_version System.version()
+  @compiled_otp_version System.otp_release()
+
   def start_mix do
     # FIXME: Private API
     Mix.start()
@@ -13,6 +16,11 @@ defmodule ElixirLS.Utils.Launch do
   def print_versions do
     IO.inspect(System.build_info()[:build], label: "Elixir version")
     IO.inspect(System.otp_release(), label: "Erlang version")
+
+    IO.puts(
+      "ElixirLS compiled with Elixir #{@compiled_elixir_version}" <>
+        " and erlang #{@compiled_otp_version}"
+    )
   end
 
   def language_server_version do