Add explicit Release/Debug configurations to all.gyp to appease xcodebuild

build/all.gyp

 # Copyright 2011 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.
 
 {
   'targets': [
     {
       'target_name': 'All',
       'type': 'none',
       'dependencies': [
         '../preparser/preparser.gyp:*',
         '../samples/samples.gyp:*',
         '../src/d8.gyp:d8',
         '../test/cctest/cctest.gyp:*',
       ],
+      # Yes, even a meta target has configurations. Xcode insists on this.
+      'configurations': {
+        'Debug': {},
+        'Release': {},
+      }
     }
   ]
 }