Clang update script: disable --with-android with LLVM_FORCE_HEAD_REVISION

tools/clang/scripts/update.sh

 #!/usr/bin/env bash
 # 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.
 
 # This script will check out llvm and clang into third_party/llvm and build it.
 
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://code.google.com/p/chromium/wiki/UpdatingClang
 # Reverting problematic clang rolls is safe, though.
@@ skipping 138 matching lines @@
   esac
   shift
 done
 
 if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
   force_local_build=yes
 
   # Skip local patches when using HEAD: they probably don't apply anymore.
   with_patches=
 
+  if ! [[ "$GYP_DEFINES" =~ .*OS=android.* ]]; then
+    # Only build the Android ASan rt when targetting Android.
+    with_android=
+  fi
+
   echo "LLVM_FORCE_HEAD_REVISION was set; using r${CLANG_REVISION}"
 fi
 
 if [[ -n "$if_needed" ]]; then
   if [[ "${OS}" == "Darwin" ]]; then
     # clang is used on Mac.
     true
   elif [[ "$GYP_DEFINES" =~ .*(clang|tsan|asan|lsan|msan)=1.* ]]; then
     # clang requested via $GYP_DEFINES.
     true
@@ skipping 790 matching lines @@
 
 if [[ -n "$run_tests" ]]; then
   # Run Chrome tool tests.
   ninja -C "${LLVM_BUILD_DIR}" cr-check-all
   # Run the LLVM and Clang tests.
   ninja -C "${LLVM_BUILD_DIR}" check-all
 fi
 
 # After everything is done, log success for this revision.
 echo "${CLANG_AND_PLUGINS_REVISION}" > "${STAMP_FILE}"