Teach install-build-deps.sh --arm how to install the arm root image.

build/install-build-deps.sh

 #!/bin/bash -e
 
 # 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.
 
 # Script to install everything needed to build chromium (well, ideally, anyway)
 # See http://code.google.com/p/chromium/wiki/LinuxBuildInstructions
 # and http://code.google.com/p/chromium/wiki/LinuxBuild64Bit
 
@@ skipping 231 matching lines @@
   echo "The following command failed: " ${new_list_cmd}
   echo
   echo "It produces the following output:"
   yes n | $new_list_cmd || true
   echo
   echo "You will have to install the above packages yourself."
   echo
   exit 100
 fi
 
+# Install arm root image
+if test "$do_inst_arm" = "1"; then
+  # As well as the arm toolchain packages we also need a recent arm root
+  # image to build against (using --sysroot).  We could construct this
+  # from scratch based on the current state or precise/arm but for
+  # consistency we currently use a pre-built root image which was constructed
+  # for building trusted NaCl code.
+  CHROME_ROOT="$(dirname ${BASH_SOURCE[0]})"
+  CHROME_ROOT="$(dirname ${CHROME_ROOT})"
+  SYSROOT="${CHROME_ROOT}/arm-sysroot"
+  TC_URL_PREFIX=https://commondatastorage.googleapis.com/nativeclient-archive2/toolchain
+  TC_REV=8001
+  TC_URL=${TC_URL_PREFIX}/${TC_REV}/naclsdk_linux_arm-trusted.tgz
+
+  INSTALL_ROOT="yes"
+  STAMP="${SYSROOT}/.stamp"
+  if [ -f "${STAMP}" ]; then
+    if [ "${TC_URL}" = $(cat ${STAMP}) ]; then
+      INSTALL_ROOT="no"
+    fi
+  fi
+
+  if [ $INSTALL_ROOT = "no" ]; then
+    echo "ARM root image already up-to-date."
+  else
+    echo "Installing ARM root image."
+    mkdir -p ${SYSROOT}
+    tarball=${SYSROOT}/naclsdk_linux_arm-trusted.tgz
+    set -x
+    curl -L ${TC_URL} -o ${tarball}
+    tar xf ${tarball} -C ${SYSROOT}
+    rm ${tarball}
+    echo -n "${TC_URL}" > "${STAMP}"
+  fi
+fi
+
 # Install 32bit backwards compatibility support for 64bit systems
 if [ "$(uname -m)" = "x86_64" ]; then
   if test "$do_inst_lib32" != "1"
   then
     echo "NOTE: If you were expecting the option to install 32bit libs,"
     echo "please run with the --lib32 flag."
     echo
     echo "Installation complete."
     exit 0
   fi
@@ skipping 173 matching lines @@
              sed -e 's/[.]so[.][0-9].*/.so/' |
              sort -u); do
     [ "x${i##*/}" = "xld-linux.so" ] && continue
     [ -r "$i" ] && continue
     j="$(ls "$i."* | sed -e 's/.*[.]so[.]\([^.]*\)$/\1/;t;d' |
          sort -n | tail -n 1)"
     [ -r "$i.$j" ] || continue
     sudo ln -s "${i##*/}.$j" "$i"
   done
 fi