Remove Ruby version constraint workarounds

Gemfile

@@ -12,13 +12,7 @@ branch = File.read(File.expand_path("../maintenance-branch", __FILE__)).chomp
   end
 end
 
-if RUBY_VERSION < '1.9.3'
-  gem 'rake', '< 11.0.0' # rake 11 requires Ruby 1.9.3 or later
-elsif RUBY_VERSION < '2.0.0'
-  gem 'rake', '< 12.0.0' # rake 12 requires Ruby 2.0.0 or later
-else
-  gem 'rake', '> 12.3.2'
-end
+gem 'rake'
 
 if ENV['DIFF_LCS_VERSION']
   gem 'diff-lcs', ENV['DIFF_LCS_VERSION']
@@ -34,33 +28,13 @@ group :documentation do
   gem 'github-markup', :platform => :mri
 end
 
-if RUBY_VERSION < '2.0.0' || RUBY_ENGINE == 'java'
-  gem 'json', '< 2.0.0'
-else
-  gem 'json', '> 2.3.0'
-end
-
-if RUBY_VERSION < '2.2.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
-  gem 'ffi', '< 1.10'
-elsif RUBY_VERSION < '2.0'
-  gem 'ffi', '< 1.9.19' # ffi dropped Ruby 1.8 support in 1.9.19
-else
-  gem 'ffi', '~> 1.11.0'
-end
-
 if RUBY_VERSION < '2.3.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
   gem "childprocess", "< 1.0.0"
 end
 
 platforms :jruby do
-  if RUBY_VERSION < '1.9.0'
-    # Pin jruby-openssl on older J Ruby
-    gem "jruby-openssl", "< 0.10.0"
-    # Pin child-process on older J Ruby
-    gem "childprocess", "< 1.0.0"
-  else
-    gem "jruby-openssl"
-  end
+  # Pin child-process on older JRuby
+  gem "childprocess", "< 1.0.0" if RUBY_VERSION < '1.9.0'
 end
 
 gem 'simplecov', '~> 0.8'
@@ -70,14 +44,16 @@ if RUBY_VERSION >= '2.4' && RUBY_ENGINE == 'ruby'
   gem "rubocop", "~> 0.52.1"
 end
 
-gem 'test-unit', '~> 3.0' if RUBY_VERSION.to_f >= 2.2
+# Contracts gem denies that it uses Ruby 2.0 syntax
+gem 'contracts', '< 0.16' if RUBY_VERSION < '1.9.0'
 
-# Version 5.12 of minitest requires Ruby 2.4
-if RUBY_VERSION < '2.4.0'
-  gem 'minitest', '< 5.12.0'
-end
+# json 2.2.0 denies that it needs Ruby 2.0
+gem 'json', '< 2.0.0' if RUBY_VERSION < '2.0.0' || RUBY_ENGINE == 'java'
 
+# Test::Unit was removed from stdlib in Ruby 2.2
+gem 'test-unit', '~> 3.0' if RUBY_VERSION.to_f >= 2.2
 
-gem 'contracts', '< 0.16' if RUBY_VERSION < '1.9.0'
+# Minitest version 5.12.0 relies on Ruby 2.4, but denies it
+gem 'minitest', '!= 5.12.0'
 
 eval File.read('Gemfile-custom') if File.exist?('Gemfile-custom')

spec/support/aruba_support.rb

@@ -1,6 +1,8 @@
 module ArubaLoader
   extend RSpec::Support::WithIsolatedStdErr
   with_isolated_stderr do
+    # Aruba depends on FFI, but under JRuby it's not loaded for some reason
+    require 'ffi'
     require 'aruba/api'
   end
 end