[test] Add rake spec:all task which runs the tests against all iOS SDKs.

test/test/Rakefile

@@ -9,4 +9,29 @@ Motion::Project::App.setup do |app|
   app.name = 'test'
   app.frameworks += ['AddressBook', 'AddressBookUI', 'CoreData', 'CoreMIDI', 'GameKit']
   app.vendor_project('vendor/code', :static)
+  app.deployment_target = ENV['deployment_target'] if ENV['deployment_target']
+end
+
+namespace :spec do
+  desc "Run tests on all available iOS SDKs"
+  task :all do
+    sdk_versions = Dir.glob(File.join(App.config.platforms_dir, "#{App.config.deploy_platform}.platform/Developer/SDKs/#{App.config.deploy_platform}*.sdk")).map do |path|
+      File.basename(path).scan(/#{App.config.deploy_platform}(.*)\.sdk/)[0][0]
+    end
+
+    counter = 0
+    sdk_versions.each do |sdk_version|
+      App.info "Info", "Running specs on iOS #{sdk_version} SDK."
+      #sh "rake clean"
+      begin
+        sh "rake spec deployment_target=#{sdk_version}"
+      rescue RuntimeError
+        counter += $?.exitstatus
+      end
+    end
+    if counter > 0
+      App.info "Failed", "A total of #{counter} failures occurred."
+      exit counter
+    end
+  end
 end