add is_windows to option

lib/paperclip.rb

@@ -98,6 +98,7 @@ module Paperclip
       swallow_stderr: true,
       use_exif_orientation: true,
       whiny: true,
+      is_windows: Gem.win_platform?
     }
   end
 

lib/paperclip/geometry_detector_factory.rb

@@ -17,7 +17,7 @@ module Paperclip
         orientation = Paperclip.options[:use_exif_orientation] ?
           "%[exif:orientation]" : "1"
         Paperclip.run(
-          Gem.win_platform? ? "magick identify" : "identify",
+          Paperclip.options[:is_windows] ? "magick identify" : "identify",
           "-format '%wx%h,#{orientation}' :file", {
             :file => "#{path}[0]"
           }, {

lib/paperclip/processor.rb

@@ -38,7 +38,7 @@ module Paperclip
     # See Paperclip.run for the available options.
     def convert(arguments = "", local_options = {})
       Paperclip.run(
-        Gem.win_platform ? "magick convert" : "convert",
+        Paperclip.options[:is_windows] ? "magick convert" : "convert",
         arguments,
         local_options,
       )
@@ -48,7 +48,7 @@ module Paperclip
     # See Paperclip.run for the available options.
     def identify(arguments = "", local_options = {})
       Paperclip.run(
-        Gem.win_platform? ? "magick identify" : "identify",
+        Paperclip.options[:is_windows] ? "magick identify" : "identify",
         arguments,
         local_options,
       )