Exclude _GLIBCXX_DEBUG for clang.

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 2529 matching lines @@
         'conditions': [
           ['OS=="linux" or OS=="android"', {
             'target_conditions': [
               ['_toolset=="target"', {
                 'cflags': [
                   '<@(debug_extra_cflags)',
                 ],
               }],
             ],
           }],
-          ['OS=="linux"', {
+          ['OS=="linux" and clang!=1', {
             # Enable libstdc++ debugging facilities to help catch problems
             # early, see http://crbug.com/65151 .
             # TODO(phajdan.jr): Should we enable this for all of POSIX?
             'defines': ['_GLIBCXX_DEBUG=1',],
             'cflags_cc+': ['-g'],
           }],
           # Disabled on iOS because it was causing a crash on startup.
           # TODO(michelea): investigate, create a reduced test and possibly
           # submit a radar.
           ['release_valgrind_build==0 and OS!="ios"', {
@@ skipping 2121 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',
   },
 }