Rubygems 3.2 supports --platform option

Rakefile

@@ -25,7 +25,7 @@ task 'build:java' => 'date_epoch' do |t|
   gem_command = ENV["GEM_COMMAND"]
   gem_command &&= gem_command.shellsplit
   Bundler::GemHelper.instance.instance_eval do
-    sh([*(gem_command || "gem"), "build", "-V", specfile, "--", "--platform=java"]) do
+    sh([*(gem_command || "gem"), "build", "-V", "--platform=java", specfile]) do
       FileUtils.mkdir_p("pkg")
       FileUtils.mv(file_name, "pkg")
       Bundler.ui.confirm "#{spec.name} #{spec.version} built to pkg/#{file_name}."

io-console.gemspec

@@ -22,11 +22,6 @@ Gem::Specification.new do |s|
   ]
   s.extensions = %w[ext/io/console/extconf.rb]
 
-  if i = ARGV.index("--") and !(argv = ARGV[i+1..-1]).empty?
-    OptionParser.new(__FILE__) do |opt|
-      opt.on("--platform=PLATFORM") {|p| s.platform = p}
-    end.parse!(argv)
-  end
   if Gem::Platform === s.platform and s.platform =~ 'java'
     s.files.delete_if {|f| f.start_with?("ext/")}
     s.extensions.clear