Accept chardata paths in Mix.Release.make_boot_script/4 (#15573)

Found by re-running the type checker over function bodies with
spec-derived argument domains (#15559): the path argument is spec'd
Path.t() (chardata), but the body applies <> and String.to_charlist/1
to it, so a charlist path -- valid per the spec -- raised
ArgumentError. Normalize with IO.chardata_to_string/1 first, as the
Path module functions do.

Author: lukaszsamson

lib/mix/lib/mix/release.ex

@@ -609,6 +609,8 @@ defmodule Mix.Release do
   @spec make_boot_script(t, Path.t(), [{application(), mode()}], [String.t()]) ::
           :ok | {:error, String.t()}
   def make_boot_script(release, path, modes, prepend_paths \\ []) do
+    path = IO.chardata_to_string(path)
+
     with {:ok, rel_spec} <- build_release_spec(release, modes) do
       File.write!(path <> ".rel", consultable(rel_spec))