clang tot bots: let mac/win asan bots use non-stale asan runtimes

build/toolchain/toolchain.gni

 # Copyright 2015 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.
 
 # Toolchain-related configuration that may be needed outside the context of the
 # toolchain() rules themselves.
 
 import("//build_overrides/build.gni")
 import("//build/config/chrome_build.gni")
 
@@ skipping 32 matching lines @@
 }
 
 # The path to the hermetic install of Xcode. Only relevant when
 # use_system_xcode = false.
 hermetic_xcode_path =
     rebase_path("//build/${target_os}_files/Xcode.app", "", root_build_dir)
 
 declare_args() {
   if (is_clang) {
     # Clang compiler version. Clang files are placed at version-dependent paths.
-    clang_version = "4.0.0"
+    if (llvm_force_head_revision) {
+      clang_version = "5.0.0"
+    } else {
+      # TODO(thakis): Remove this branch the next time clang rolls.
+      clang_version = "4.0.0"
+    }
   }
 }
 
 # Check target_os here instead of is_ios as this file is loaded for secondary
 # toolchain (host toolchain in particular) but the argument is the same for
 # all toolchains.
 assert(!use_xcode_clang || target_os == "ios",
        "Using Xcode's clang is only supported in iOS builds")
 
 # Subdirectory within root_out_dir for shared library files.
@@ skipping 42 matching lines @@
   _tool_wrapper_path =
       rebase_path("//build/toolchain/win/tool_wrapper.py", root_build_dir)
 
   stamp_command = "$python_path $_tool_wrapper_path stamp {{output}}"
   copy_command =
       "$python_path $_tool_wrapper_path recursive-mirror {{source}} {{output}}"
 } else {
   stamp_command = "touch {{output}}"
   copy_command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
 }