[Validator] Finally make the xcodebuild failure test work reliably

lib/cocoapods/validator.rb

@@ -521,11 +521,9 @@ module Pod
     def xcodebuild
       command = 'xcodebuild clean build -target Pods CODE_SIGN_IDENTITY=-'
       command << ' -sdk iphonesimulator' if consumer.platform_name == :ios
+      output, status = _xcodebuild "#{command} 2>&1"
 
-      UI.puts command if config.verbose?
-      output = `#{command} 2>&1`
-
-      unless $?.success?
+      unless status.success?
         message = 'Returned a unsuccessful exit code.'
         message += ' You can use `--verbose` for more information.' unless config.verbose?
         error('xcodebuild', message)
@@ -534,6 +532,17 @@ module Pod
       output
     end
 
+    # Executes the given command in the current working directory.
+    #
+    # @return [(String, Status)] The output of the given command and its
+    #         resulting status.
+    #
+    def _xcodebuild(command)
+      UI.puts command if config.verbose
+      output = `#{command}`
+      return output, $?
+    end
+
     #-------------------------------------------------------------------------#
   end
 end

spec/unit/validator_spec.rb

@@ -364,7 +364,9 @@ module Pod
         validator.stubs(:check_file_patterns)
         validator.stubs(:validate_url)
         validator.stubs(:`).returns('Output')
-        $?.stubs(:success?).returns(false)
+        status = mock()
+        status.stubs(:success?).returns(false)
+        validator.stubs(:_xcodebuild).returns(['Output', status])
         validator.validate
         first = validator.results.map(&:to_s).first
         first.should.include '[xcodebuild] Returned a unsuccessful exit code'