Put the syzygy targets behind a 'syzygy_optimize' flag.

chrome/chrome_syzygy.gyp

 # Copyright (c) 2011 The Chromium 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': [
     ['syzyasan==1', {
       'variables': {
         'dest_dir': '<(PRODUCT_DIR)/syzygy',
         'syzygy_exe_dir': '<(DEPTH)/third_party/syzygy/binaries/exe',
       },
@@ skipping 13 matching lines @@
               'files': [
                 '<(syzygy_exe_dir)/agent_logger.exe',
                 '<(syzygy_exe_dir)/syzyasan_rtl.dll',
                 '<(syzygy_exe_dir)/syzyasan_rtl.dll.pdb',
               ],
             },
           ],
         },
       ],
     }],
-    ['OS=="win" and fastbuild==0', {
+    ['OS=="win" and fastbuild==0 and (syzygy_optimize==1 or syzyasan==1)', {
       'variables': {
         'dll_name': 'chrome',
       },
       'targets': [
         {
           'target_name': 'chrome_dll_syzygy',
           'type': 'none',
           'sources' : [],
           'includes': [
             'chrome_syzygy.gypi',
           ],
         },
       ],
     }],
     # Note, not else.
     ['OS=="win" and fastbuild==0 and chrome_multiple_dll==1 and '
-        '(syzyasan!=1 or buildtype!="Official")', {
+        '(syzyasan!=1 or buildtype!="Official") and '
+        '(syzygy_optimize==1 or syzyasan==1)', {

[chrisha, 2014/03/14 22:01:36]

A comment to describe this logic? It's a bit tortuous.... :)

[Sébastien Marchand, 2014/03/17 17:41:14]

I've refactored this file a little bit.

       'variables': {
         'dll_name': 'chrome_child',
       },
       'targets': [
         {
           'target_name': 'chrome_child_dll_syzygy',
           'type': 'none',
           'sources' : [],
           'includes': [
             'chrome_syzygy.gypi',
@@ skipping 24 matching lines @@
                   '<(PRODUCT_DIR)/chrome_child.dll.pdb',
                 ],
               },
             ],
           }],
         }],
       ],
     }],
   ],
 }