linux: enable safe identical code folding for release builds

build/common.gypi

 # 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.
 
 # 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 1106 matching lines @@
                 'cflags!': [
                   '-fno-ident',
                 ],
               }],
               ['profiling==1', {
                 'cflags': [
                   '-fno-omit-frame-pointer',
                   '-g',
                 ],
               }],
+              # At gyp time, we test the linker for ICF support; this flag
+              # is then provided to us by gyp.  (Currently only gold supports
+              # an --icf flag.)
+              ['LINKER_SUPPORTS_ICF==1', {
+                'ldflags': [
+                  '-Wl,--icf=safe',
+                ]
+              }],
             ]
           },
         },
         'variants': {
           'coverage': {
             'cflags': ['-fprofile-arcs', '-ftest-coverage'],
             'ldflags': ['-fprofile-arcs'],
           },
           'profile': {
             'cflags': ['-pg', '-g'],
@@ skipping 564 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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 # tab-width:2
 # indent-tabs-mode:nil
 # End:
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