An option and a tentative fix for 32-bit Clang build.

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 1416 matching lines @@
         # See http://crbug.com/145503.
         'component': "static_library",
       }],
       ['tsan==1', {
         'clang%': 1,
       }],
 
       ['OS=="linux" and clang_type_profiler==1', {
         'clang%': 1,
         'clang_use_chrome_plugins%': 0,
-        'make_clang_dir%': 'third_party/llvm-allocated-type/Linux_x64',
+        'conditions': [
+          ['host_arch=="x64"', {
+            'make_clang_dir%': 'third_party/llvm-allocated-type/Linux_x64',
+          }],
+          ['host_arch=="ia32"', {
+            # 32-bit Clang is unsupported.  It may not build.  Put your 32-bit
+            # Clang in this directory at your own risk if needed for some
+            # purpose (e.g. to compare 32-bit and 64-bit behavior like memory
+            # usage).  Any failure by this compiler should not close the tree.
+            'make_clang_dir%': 'third_party/llvm-allocated-type/Linux_ia32',
+          }],
+        ],
       }],
 
       # On valgrind bots, override the optimizer settings so we don't inline too
       # much and make the stacks harder to figure out.
       #
       # TODO(rnk): Kill off variables that no one else uses and just implement
       # them under a build_for_tool== condition.
       ['build_for_tool=="memcheck" or build_for_tool=="tsan"', {
         # gcc flags
         'mac_debug_optimization': '1',
@@ skipping 165 matching lines @@
         'cflags_cc+': [
           '-frtti',
           '-gline-tables-only',
           '-fintercept-allocation-functions',
         ],
         'defines': ['TYPE_PROFILING'],
         'dependencies': [
           '<(DEPTH)/base/allocator/allocator.gyp:type_profiler',
         ],
       }],
+      ['OS=="linux" and clang==1 and host_arch=="ia32"', {
+        # TODO(dmikurube): Remove -Wno-sentinel when Clang/LLVM is fixed.
+        # See http://crbug.com/162818.
+        'cflags+': ['-Wno-sentinel'],
+      }],
       ['OS=="win" and "<(msbuild_toolset)"!=""', {
         'msbuild_toolset': '<(msbuild_toolset)',
       }],
       ['branding=="Chrome"', {
         'defines': ['GOOGLE_CHROME_BUILD'],
       }, {  # else: branding!="Chrome"
         'defines': ['CHROMIUM_BUILD'],
       }],
       ['OS=="mac" and component=="shared_library"', {
         'xcode_settings': {
@@ skipping 2352 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',
   },
 }