[build] Use sysroot for linux compilation with clang

DEPS

 # Note: The buildbots evaluate this file with CWD set to the parent
 # directory and assume that the root of the checkout is in ./v8/, so
 # all paths in here must match this assumption.
 
 vars = {
   "git_url": "https://chromium.googlesource.com",
 }
 
 deps = {
   "v8/build":
@@ skipping 174 matching lines @@
     "pattern": ".",
     "action": [ "download_from_google_storage",
                 "--no_resume",
                 "--platform=linux*",
                 "--no_auth",
                 "--bucket", "chromium-gn",
                 "-s", "v8/buildtools/linux64/gn.sha1",
     ],
   },
   {
+    # Downloads the current stable linux sysroot to build/linux/ if needed.
+    # This sysroot updates at about the same rate that the chrome build deps
+    # change.
+    'name': 'sysroot',
+    'pattern': '.',
+    'action': [
+        'python',
+        'v8/build/linux/sysroot_scripts/install-sysroot.py',
+        '--running-as-hook',
+    ],
+  },
+  {
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'v8/gypfiles/vs_toolchain.py', 'update'],
   },
   # Pull binutils for linux, enabled debug fission for faster linking /
   # debugging when used with clang on Ubuntu Precise.
   # https://code.google.com/p/chromium/issues/detail?id=352046
   {
     'name': 'binutils',
@@ skipping 16 matching lines @@
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "v8/gypfiles/gyp_v8"],
   },
 ]