Add support for downloading 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 = {
   # Remember to keep the revision in sync with the Makefile.
   "v8/build/gyp":
     Var("git_url") + "/external/gyp.git@a3e2a5caf24a1e0a45401e09ad131210bf16b852",
   "v8/third_party/icu":
     Var("git_url") + "/chromium/deps/icu52.git@26d8859357ac0bfb86b939bf21c087b8eae22494",
   "v8/buildtools":
     Var("git_url") + "/chromium/buildtools.git@fb782d4369d5ae04f17a2fceef7de5a63e50f07b",
   "v8/testing/gtest":
     Var("git_url") + "/external/googletest.git@4650552ff637bb44ecf7784060091cbed3252211",
   "v8/testing/gmock":
     Var("git_url") + "/external/googlemock.git@896ba0e03f520fb9b6ed582bde2bd00847e3c3f2",
+  "v8/tools/clang":
+    Var("git_url") + "/chromium/src/tools/clang.git@327e26ee7f6ae6f86fb335113b46cb86ed3cb0dc",

[Michael Achenbach, 2014/11/26 15:08:34]

Be aware of make dependencies...

[jochen (gone - plz use gerrit), 2014/11/27 10:02:39]

everybody should be using gclient sync, no?

[Michael Achenbach, 2014/11/27 10:13:05]

I can't speak for other people. The best way to enforce that is to remove the
dependencies target from the Makefile. I'll do that and wait for complaints...

 }
 
 deps_os = {
   "android": {
     "v8/third_party/android_tools":
       Var("git_url") + "/android_tools.git@31869996507de16812bb53a3d0aaa15cd6194c16",
   },
   "win": {
     "v8/third_party/cygwin":
       Var("git_url") + "/chromium/deps/cygwin.git@06a117a90c15174436bfa20ceebbfdf43b7eb820",
@@ skipping 44 matching lines @@
     "pattern": ".",
     "action": [ "download_from_google_storage",
                 "--no_resume",
                 "--platform=linux*",
                 "--no_auth",
                 "--bucket", "chromium-clang-format",
                 "-s", "v8/buildtools/linux64/clang-format.sha1",
     ],
   },
   {
+    # Pull clang if needed or requested via GYP_DEFINES.

[Michael Achenbach, 2014/11/26 15:08:34]

I don't understand how this is dependent on GYP_DEFINES. Is the update script
only called if clang=1 or always?

[jochen (gone - plz use gerrit), 2014/11/27 10:02:39]

it internally checks the gyp defines

+    # Note: On Win, this should run after win_toolchain, as it may use it.
+    '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/build/gyp_v8"],
   },
 ]