Equalise hello-world-windows and hello-moon-windows

These are both no-op buildpacks, make them syntactically the same.

buildpacks/hello-moon-windows/bin/build.bat

@@ -2,10 +2,13 @@
 
 echo --- Hello Moon buildpack
 
-set env_dir=%2\env
+:: INPUT ARGUMENTS
+set platform_dir=%2
+set env_dir=%platform_dir%\env
 set layers_dir=%1
 set plan_path=%3
 
+:: ENV VARS
 echo      env_dir: %env_dir%
 echo      env_vars:
 for /f "tokens=*" %%f in ('dir /s /q /b %env_dir%') do (
@@ -17,7 +20,10 @@ for /f "tokens=*" %%o in ('set') do (
     echo        %%o
 )
 
+:: LAYERS
 echo      layers_dir: %layers_dir%
+
+:: PLAN
 echo      plan_path: %plan_path%
 echo      plan contents:
 for /f "tokens=*" %%o in ('type %plan_path%') do (