only use gold-specific flags for the target linker

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 3360 matching lines @@
           ['linux_keep_shadow_stacks==1', {
             'defines': ['KEEP_SHADOW_STACKS'],
             'cflags': [
               '-finstrument-functions',
               # Allow mmx intrinsics to inline, so that the compiler can expand
               # the intrinsics.
               '-finstrument-functions-exclude-file-list=mmintrin.h',
             ],
           }],
           ['linux_use_gold_flags==1', {
-            '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
-              '-Wl,--threads',
-              '-Wl,--thread-count=4',
+            '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',
+                ],
+              }],
             ],
             'conditions': [
               ['release_valgrind_build==0', {
                 'target_conditions': [
                   ['_toolset=="target"', {
                     'ldflags': [
                       # There seems to be a conflict of --icf and -pie
                       # in gold which can generate crashy binaries. As
                       # a security measure, -pie takes precendence for
                       # now.
@@ skipping 1254 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',
   },
 }