Require opal/platfrom where OPAL_PLATFORM is used

Author: elia

lib-opal/opal/rspec/fixes/opal.rb

@@ -1,3 +1,5 @@
+require 'opal/platform'
+
 class IO
   def closed?
     true

lib/opal/rspec/runner.rb

@@ -78,7 +78,6 @@ def initialize(&block)
         options = []
         options << '--arity-check' if arity_checking?
         options += ['--runner', runner] unless runner.empty?
-        options << '-ropal/platform'
         options << '-ropal-rspec'
         options << '--missing-require=ignore'
         options += @legacy_server_proxy.to_cli_options

spec-opal/spec_helper.rb

@@ -1,5 +1,4 @@
 require 'opal/rspec/async'
-require 'opal/platform'
 
 RSpec::configure do |config|
   config.filter_run_including focus: true