Make minidump_stackwalk compile with target_arch=ia32 on a linux x64 host.

breakpad/breakpad_tools.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.
 
 {
   'conditions': [
     ['OS=="linux" or OS=="android"', {
       'variables': {
         'host_arch': '<!(uname -m)',
       },
       'conditions': [
         ['host_arch=="x86_64"', {
           'cflags!': ['-m32', '-march=pentium4', '-msse2', '-mfpmath=sse'],
           'ldflags!': ['-m32'],
           'cflags': ['-O2'],
           'include_dirs!': ['/usr/include32'],
+          'conditions': [
+            ['target_arch=="ia32" and sysroot!=""', {
+              'cflags!': ['--sysroot=<(sysroot)'],
+            }],
+          ],
         }],
       ],
     }],
     ['OS=="android"', {
       'toolsets': ['host'],
       'defines': ['__ANDROID__'],
     }],
     ['clang==1', {
       'cflags': ['-Wno-tautological-constant-out-of-range-compare'],
       'xcode_settings': {
         'WARNING_CFLAGS': ['-Wno-tautological-constant-out-of-range-compare'],
       },
     }],
   ],
   'include_dirs': [
     'src',
     'src/third_party',
   ],
 }