[build] Disable linker threading in LTO builds, as it causes intermittent link failures.

build/toolchain.gypi

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 1131 matching lines @@
               ['android_full_debug==0', {
                 # Disable full debug if we want a faster v8 in a debug build.
                 # TODO(2304): pass DISABLE_DEBUG_ASSERT instead of hiding DEBUG.
                 'defines!': [
                   'DEBUG',
                   'ENABLE_SLOW_DCHECKS',
                 ],
               }],
             ],
           }],
-          ['linux_use_gold_flags==1', {
+          # TODO(pcc): Re-enable in LTO builds once we've fixed the intermittent
+          # link failures (crbug.com/513074).
+          ['linux_use_gold_flags==1 and use_lto==0', {
             'target_conditions': [
               ['_toolset=="target"', {
                 'ldflags': [
                   # Experimentation found that using four linking threads
                   # saved ~20% of link time.
                   # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
                   # Only apply this to the target linker, since the host
                   # linker might not be gold, but isn't used much anyway.
                   '-Wl,--threads',
                   '-Wl,--thread-count=4',
@@ skipping 89 matching lines @@
           ['v8_enable_slow_dchecks==1', {
             'defines': [
               'ENABLE_SLOW_DCHECKS',
             ],
           }],
         ],  # conditions
       },  # Release
     },  # configurations
   },  # target_defaults
 }