Enable ARM/linux cross compile to use clang.

build/linux/install-arm-sysroot.py

 #!/usr/bin/env python
 # 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 ARM root image for cross building of ARM chrome on linux.
 This script can be run manually but is more often run as part of gclient
 hooks. When run from hooks this script should be a no-op on non-linux
 platforms.
 
 The sysroot image could be constructed from scratch based on the current
 state or precise/arm but for consistency we currently use a pre-built root
 image which was originally designed for building trusted NaCl code. The image
 will normally need to be rebuilt every time chrome's build dependancies are
 changed.
 
 Steps to rebuild the arm sysroot image:
 
 - cd $SRC/native_client
 - ./tools/trusted_cross_toolchains/trusted-toolchain-creator.armel.precise.sh \
     UpdatePackageLists
 - ./tools/trusted_cross_toolchains/trusted-toolchain-creator.armel.precise.sh \
     BuildJail $SRC/out/arm-sysroot.tar.gz
 - gsutil cp -a public-read $SRC/out/arm-sysroot.tar.gz \
     nativeclient-archive2/toolchain/$NACL_REV/sysroot-arm-trusted.tgz
 """
 
+# TODO(sbc): merge this script into:
+#  chrome/installer/linux/sysroot_scripts/install-debian.wheezy.sysroot.py
+
+import hashlib
 import os
 import shutil
 import subprocess
 import sys
 
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 URL_PREFIX = 'https://storage.googleapis.com'
-URL_PATH = 'nativeclient-archive2/toolchain'
-REVISION = 13035
-TARBALL = 'sysroot-arm-trusted.tgz'
+URL_PATH = 'chrome-linux-sysroot/toolchain'
+REVISION = 285950
+TARBALL = 'debian_wheezy_arm_sysroot.tgz'
+TARBALL_SHA1SUM = 'fc2f54db168887c5190c4c6686c869bedf668b4e'
+
+
+def get_sha1(filename):
+  sha1 = hashlib.sha1()
+  with open(filename, 'rb') as f:
+    while True:
+      # Read in 1mb chunks, so it doesn't all have to be loaded into memory.
+      chunk = f.read(1024*1024)
+      if not chunk:
+        break
+      sha1.update(chunk)
+  return sha1.hexdigest()
+
 
 def main(args):
   if '--linux-only' in args:
     # This argument is passed when run from the gclient hooks.
     # In this case we return early on non-linux platforms
     # or if GYP_DEFINES doesn't include target_arch=arm
     if not sys.platform.startswith('linux'):
       return 0
 
     if "target_arch=arm" not in os.environ.get('GYP_DEFINES', ''):
@@ skipping 14 matching lines @@
   if os.path.isdir(sysroot):
     shutil.rmtree(sysroot)
   os.mkdir(sysroot)
   tarball = os.path.join(sysroot, TARBALL)
   curl = ['curl', '--fail', '-L', url, '-o', tarball]
   if os.isatty(sys.stdout.fileno()):
     curl.append('--progress')
   else:
     curl.append('--silent')
   subprocess.check_call(curl)
+  sha1sum = get_sha1(tarball)
+  if sha1sum != TARBALL_SHA1SUM:
+    print 'Tarball sha1sum is wrong.'
+    print 'Expected %s, actual: %s' % (TARBALL_SHA1SUM, sha1sum)
+    return 1
   subprocess.check_call(['tar', 'xf', tarball, '-C', sysroot])
   os.remove(tarball)
 
   with open(stamp, 'w') as s:
     s.write(url)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))