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

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 0a241b5b028e61934470358ffa738b11d1419ea2..be9ae64742b34db4b6753bc2d776cb25eb11d360 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -1437,7 +1437,18 @@
       ['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
@@ -1623,6 +1634,11 @@
           '<(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)',
       }],