Fix libc++ ARM build

third_party/libc++/BUILD.gn

 # Copyright 2015 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.
 
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
 # Sanitizer builds need to override operator new, operator delete, and
 # some exception handling symbols, so libc++ must be a shared library
 # to prevent duplicate symbol errors when linking.
@@ skipping 28 matching lines @@
   cflags = [
     "-fPIC",
     "-fstrict-aliasing",
   ]
   cflags_cc = [
     "-nostdinc++",
     "-isystem" + rebase_path("trunk/include", root_build_dir),
     "-isystem" + rebase_path("../libc++abi/trunk/include", root_build_dir),
     "-std=c++11",
   ]
+  if (is_linux && target_cpu == "arm") {
+    cflags_c = [ "-isystem" + rebase_path("../libunwind/trunk/include", root_build_dir) ]
+    cflags_cc += [ "-isystem" + rebase_path("../libunwind/trunk/include", root_build_dir) ]
+  }
 }
 
 config("no_libstdcpp") {
   # Make sure we don't link against libc++ or libstdc++.
   ldflags = [ "-nodefaultlibs" ]
 
   # Unfortunately, there's no way to disable linking against just
   # libc++ (besides using clang instead of clang++); -nodefaultlibs
   # removes all of the default libraries, so add back the ones that we
   # need.
@@ skipping 92 matching lines @@
       # Normally the generator takes care of RPATH. Our case is special because
       # the generator is unaware of the libc++.so dependency. Note that setting
       # RPATH here is a potential security issue. See the following for another
       # example of this issue: https://code.google.com/p/gyp/issues/detail?id=315
       "-Wl,-rpath,\$ORIGIN/",
     ]
   }
 
   lib_dirs = [ root_build_dir ]
 }