Add gn Blink GC plugin options

build/toolchain/win/BUILD.gn

 # Copyright (c) 2013 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.
 
+import("//build/config/clang/clang.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 import("//build/toolchain/concurrent_links.gni")
 
 # Should only be running on Windows.
 assert(is_win)
 
 # Setup the Visual Studio state.
@@ skipping 48 matching lines @@
   } else {
     cl = invoker.cl
   }
 
   if (use_lld) {
     if (host_os == "win") {
       lld_link = "lld-link.exe"
     } else {
       lld_link = "lld-link"
     }
-    prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                         root_build_dir)
+    prefix = rebase_path("$clang_base_path/bin", root_build_dir)
 
     # lld-link includes a replacement for lib.exe that can produce thin
     # archives and understands bitcode (for lto builds).
     lib = "$prefix/$lld_link /lib /llvmlibthin"
     link = "$prefix/$lld_link"
   } else {
     lib = "lib.exe"
     link = "link.exe"
   }
 
@@ skipping 221 matching lines @@
   msvc_toolchain("x86") {
     environment = "environment.x86"
     toolchain_cpu = "x86"
     cl = "${goma_prefix}\"${x86_toolchain_data.vc_bin_dir}/cl.exe\""
     is_clang = false
   }
 
   msvc_toolchain("clang_x86") {
     environment = "environment.x86"
     toolchain_cpu = "x86"
-    prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                         root_build_dir)
+    prefix = rebase_path("$clang_base_path/bin", root_build_dir)
     cl = "${goma_prefix}$prefix/${clang_cl}"
     toolchain_os = "win"
     is_clang = true
     sys_include_flags = "${x86_toolchain_data.include_flags}"
   }
 }
 
 # 64-bit toolchains.
 x64_toolchain_data = exec_script("setup_toolchain.py",
                                  [
@@ skipping 23 matching lines @@
     # This shares a name with a global and forward_variables_from won't clobber
     # the existing value, so we need to set it explicitly.
     if (defined(invoker.is_component_build)) {
       is_component_build = invoker.is_component_build
     }
   }
 
   msvc_toolchain("clang_" + target_name) {
     environment = "environment.x64"
     toolchain_cpu = "x64"
-    prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                         root_build_dir)
+    prefix = rebase_path("$clang_base_path/bin", root_build_dir)
     cl = "${goma_prefix}$prefix/${clang_cl}"
     toolchain_os = "win"
     is_clang = true
     sys_include_flags = "${x64_toolchain_data.include_flags}"
 
     # This shares a name with a global and forward_variables_from won't clobber
     # the existing value, so we need to set it explicitly.
     if (defined(invoker.is_component_build)) {
       is_component_build = invoker.is_component_build
     }
@@ skipping 42 matching lines @@
 
   msvc_toolchain("winrt_x64") {
     environment = "environment.winrt_x64"
     cl = "${goma_prefix}\"${vc_bin_dir}/cl.exe\""
     is_clang = false
 
     toolchain_cpu = "x64"
     toolchain_os = current_os
   }
 }