fix nerves.system.shell for mac os

CHANGELOG.md

@@ -6,6 +6,7 @@
     * Fix artifact archiver to use `Artifact.download_name/1` instead of 
       `Artifact.name/1`. Fixes issues with the Docker provider and
       `mix nerves.artifact`
+    * Fix issue with `nerves.system.shell` not rendering properly
 
 ## Nerves v0.9.3
 

lib/mix/nerves/shell.ex

@@ -9,8 +9,16 @@ defmodule Mix.Nerves.Shell do
     stdin_port = Port.open({:spawn, "tty_sl -c -e"}, [:binary, :eof, :stream, :in])
 
     # We run the command through the script command to emulate a pty
+    cmd = 
+      "script -q /dev/null " <>
+      case Nerves.Env.host_os() do
+        "linux" ->
+          "-c \"#{command}\""
+        _ -> "#{command}"
+      end
+
     cmd_port =
-      Port.open({:spawn, "script -q /dev/null -c \"#{command}\" "}, [
+      Port.open({:spawn, cmd}, [
         :binary,
         :eof,
         :stream,