3rd way of grabbing libc++ headers

tools/clang/scripts/update.sh

 #!/usr/bin/env bash
 # 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.
 
 # This script will check out llvm and clang into third_party/llvm and build it.
 
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://code.google.com/p/chromium/wiki/UpdatingClang
 # Reverting problematic clang rolls is safe, though.
@@ skipping 397 matching lines @@
 STRIP_FLAGS=
 if [ "${OS}" = "Darwin" ]; then
   # See http://crbug.com/256342
   STRIP_FLAGS=-x
 
   cp libcxxbuild/libc++.1.dylib Release+Asserts/bin
 fi
 strip ${STRIP_FLAGS} Release+Asserts/bin/clang
 popd
 
+# Copy libc++ headers, to make --stdlib=libc++ work for iOS.
+make -C "${LIBCXX_DIR}" \
+    installheaders HEADER_DIR="${PWD}/${LLVM_BUILD_DIR}/Release+Asserts/include"
+
 if [[ -n "${with_android}" ]]; then
   # Make a standalone Android toolchain.
   ${ANDROID_NDK_DIR}/build/tools/make-standalone-toolchain.sh \
       --platform=android-14 \
       --install-dir="${LLVM_BUILD_DIR}/android-toolchain" \
       --system=linux-x86_64 \
       --stl=stlport
 
   # Android NDK r9d copies a broken unwind.h into the toolchain, see
   # http://crbug.com/357890
@@ skipping 32 matching lines @@
       "${TOOL_SRC_DIR}/tests/test.sh" "${LLVM_BUILD_DIR}/Release+Asserts"
     fi
   done
   pushd "${LLVM_BUILD_DIR}"
   ${MAKE} check-all
   popd
 fi
 
 # After everything is done, log success for this revision.
 echo "${CLANG_AND_PLUGINS_REVISION}" > "${STAMP_FILE}"