Do not use bundled gold when using GCC LTO.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 4521 matching lines @@
                   }],
                 ],
               }],
             ],
           }],
           ['linux_use_bundled_binutils==1', {
             'cflags': [
               '-B<!(cd <(DEPTH) && pwd -P)/<(binutils_dir)',
             ],
           }],
-          ['linux_use_bundled_gold==1', {
+          ['linux_use_bundled_gold==1 and \
+            not (clang==0 and (use_lto==1 or use_lto_o2==1))', {

[Nico, 2015/04/16 19:17:12]

I think the python style guide prefers

  'abc'
  'def'

over

  'abc\
   def'

[pcc, 2015/04/16 19:45:15]

Done.

             # Put our binutils, which contains gold in the search path. We pass
             # the path to gold to the compiler. gyp leaves unspecified what the
             # cwd is when running the compiler, so the normal gyp path-munging
             # fails us. This hack gets the right path.
+            #
+            # Disabled when using GCC LTO because GCC also uses the -B search
+            # path at link time to find "as", and our bundled "as" can only
+            # target x86.
             'ldflags': [
               '-B<!(cd <(DEPTH) && pwd -P)/<(binutils_dir)',
             ],
           }],
           # Some binutils 2.23 releases may or may not have new dtags enabled,
           # but they are all compatible with --disable-new-dtags,
           # because the new dynamic tags are not created by default.
           ['binutils_version>=223', {
             # Newer binutils don't set DT_RPATH unless you disable "new" dtags
             # and the new DT_RUNPATH doesn't work without --no-as-needed flag.
@@ skipping 1545 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }