Use depot_tools toolchain, remove now unneeded code, fix not including path to win sdk tools

build/config/compiler/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/android/config.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 
 # compiler ---------------------------------------------------------------------
@@ skipping 18 matching lines @@
   # GCC flags, and then we handle the other non-Windows platforms specifically
   # below.
   if (is_win) {
     # Windows compiler flags setup.
     # -----------------------------
     cflags += [
       "/Gy",  # Enable function-level linking.
       "/GS",  # Enable buffer security checking.
       "/EHsc",  # Assume C functions can't throw exceptions and don't catch
                 # structured exceptions (only C++ ones).
+      "/FS",  # Preserve previous PDB behavior.
     ]
   } else {
     # Common GCC compiler flags setup.
     # --------------------------------
     cflags += [
       "-fno-strict-aliasing",  # See http://crbug.com/32204
       "-fvisibility=hidden",
     ]
     cflags_cc += [
       "-fno-exceptions",
@@ skipping 623 matching lines @@
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }