Use IEX_WITH_WERL environment variable to enable --werl by default.

Author: orderthruchaos

bin/iex.bat

@@ -1,2 +1,4 @@
 @if defined ELIXIR_CLI_ECHO (@echo on) else  (@echo off)
-call "%~dp0\elixir.bat" +iex --erl "-user Elixir.IEx.CLI" --no-halt %ELIXIR_IEX_FLAGS% %*
+@if defined IEX_WITH_WERL (@set __ELIXIR_IEX_FLAGS=--werl) else (set __ELIXIR_IEX_FLAGS=)
+call "%~dp0\elixir.bat" +iex --erl "-user Elixir.IEx.CLI" --no-halt %__ELIXIR_IEX_FLAGS% %*
+@set __ELIXIR_IEX_FLAGS=