Split the GN 'snapshot_toolchain' logic out into an include file.

BUILD.gn

 # Copyright 2014 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/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 # Because standalone V8 builds are not supported, assume this is part of a
 # Chromium build.
 import("//build/module_args/v8.gni")
 
+import("snapshot_toolchain.gni")
+
 # TODO(jochen): These will need to be user-settable to support standalone V8
 # builds.
 v8_deprecation_warnings = false
 v8_enable_disassembler = false
 v8_enable_gdbjit = false
 v8_enable_handle_zapping = true
 v8_enable_i18n_support = true
 v8_enable_verify_heap = false
 v8_interpreted_regexp = false
 v8_object_print = false
 v8_postmortem_support = false
 v8_use_snapshot = true
 v8_random_seed = "314159265"
 v8_toolset_for_d8 = "host"
 
 if (is_msan) {
   # Running the V8-generated code on an ARM simulator is a powerful hack that
   # allows the tool to see the memory accesses from JITted code. Without this
   # flag, JS code causes false positive reports from MSan.
   v8_target_arch = "arm64"
 } else {
   v8_target_arch = target_cpu
 }
 
-# The snapshot needs to be compiled for the host, but compiled with
-# a toolchain that matches the bit-width of the target.
-#
-# TODO(GYP): For now we only support 32-bit little-endian target builds from an
-# x64 Linux host. Eventually we need to support all of the host/target
-# configurations v8 runs on.
-if (host_cpu == "x64" && host_os == "linux") {
-  if (target_cpu == "arm" || target_cpu == "mipsel" || target_cpu == "x86") {
-    snapshot_toolchain = "//build/toolchain/linux:clang_x86"
-  } else if (target_cpu == "x64") {
-    snapshot_toolchain = "//build/toolchain/linux:clang_x64"
-  } else {
-    assert(false, "Need environment for this arch")
-  }
-} else {
-  snapshot_toolchain = default_toolchain
-}
-
 ###############################################################################
 # Configurations
 #
 config("internal_config") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   include_dirs = [ "." ]
 
   if (is_component_build) {
     defines = [
@@ skipping 1746 matching lines @@
         ":v8_base",
         ":v8_nosnapshot",
       ]
     }
 
     public_configs = [ ":external_config" ]
   }
 }
 
 if ((current_toolchain == host_toolchain && v8_toolset_for_d8 == "host") ||
+    (current_toolchain == snapshot_toolchain && v8_toolset_for_d8 == "host") ||
     (current_toolchain != host_toolchain && v8_toolset_for_d8 == "target")) {
   executable("d8") {
     sources = [
       "src/d8.cc",
       "src/d8.h",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [
@@ skipping 23 matching lines @@
     if (!is_component_build) {
       sources += [
         "$target_gen_dir/d8-js.cc",
       ]
     }
     if (v8_enable_i18n_support) {
       deps += [ "//third_party/icu" ]
     }
   }
 }