Added llvm into exceptions as we can't add README.chromium into 3rd party repository

android_webview/tools/known_issues.py

 # 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.
 
 """List of directories which are known issues for Android WebView.
 
 There are a number of directories in the Chromium tree which should be removed
 when merging into Android. Some are for licensing reasons; others are to ensure
 that the build inside the Android tree does not accidentally include the wrong
 headers.
@@ skipping 27 matching lines @@
         'breakpad',
         'chrome/installer/mac/third_party/xz',
         'chrome/test/data',
         'third_party/apple_apsl',
         'third_party/apple_sample_code',
         'third_party/bsdiff',
         'third_party/bspatch',
         'third_party/elfutils',
         'third_party/instrumented_libraries',
         'third_party/liblouis',
+        'third_party/llvm',
         'third_party/speech-dispatcher',
         'third_party/sudden_motion_sensor',
         'third_party/swiftshader',
         'third_party/talloc',
         'third_party/webdriver',
         'third_party/wtl',
         'tools/telemetry/third_party/websocket-client',
 
         # Code we don't want to build/include by accident from the main chromium
         # src/ directory.
         'third_party/libjpeg/*.[ch]',
     ],
     'third_party/icu': [
         # Incompatible code from ICU's repository.
         'source/data/brkitr',
     ],
 }
 
 KNOWN_INCOMPATIBLE['.'].extend(KNOWN_ISSUES)