Add exrm plugin to link vm.args file

if env `LINK_VM_ARGS=/path/to/vm.args` is configured.

lib/exrm/plugins/link_vm_args.ex

@@ -0,0 +1,21 @@
+defmodule ReleaseManager.Plugin.LinkVMARgs do
+  use ReleaseManager.Plugin
+  alias  ReleaseManager.Utils
+
+
+  def before_release(_), do: nil
+
+  def after_release(%Config{env: :prod, version: version, name: name}) do
+    case System.get_env "LINK_VM_ARGS" do
+      vm_args_link_destination = <<_,_::binary>> ->
+        debug "Linking vm.args file"
+        vmargs_path = Utils.rel_dest_path(Path.join([name, "releases", version, "vm.args"]))
+        if vmargs_path |> File.exists?, do: vmargs_path |> File.rm
+        File.ln_s(vm_args_link_destination, vmargs_path)
+      _ -> nil
+    end
+  end
+  def after_release(_), do: nil
+
+  def after_cleanup(_), do: nil
+end