[gn] Move build to gypfiles

test/mjsunit/mjsunit.gyp

 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'conditions': [
     ['test_isolation_mode != "noop"', {
       'targets': [
         {
           'target_name': 'mjsunit_run',
           'type': 'none',
           'dependencies': [
             '../../src/d8.gyp:d8_run',
           ],
           'includes': [
-            '../../build/features.gypi',
-            '../../build/isolate.gypi',
+            '../../gypfiles/features.gypi',
+            '../../gypfiles/isolate.gypi',
           ],
           'sources': [
             'mjsunit.isolate',
           ],
         },
       ],
     }],
   ],
 }