Move the Syzygy scripts out of //chrome/

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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 970 matching lines @@
     }
     if (is_clang) {
       deps += [ "//build/sanitizers:copy_llvm_symbolizer" ]
     }
     if (is_win && symbol_level == 2 && target_cpu == "x86" && is_syzyasan) {
       deps += [
         "//chrome/tools/build/win/syzygy:chrome_dll_syzygy",
         # TODO(GYP): Add this once it exists, https://crbug.com/619086
         # "//content/shell:content_shell_syzyasan
       ]
-      if (is_multi_dll_chrome) {
-        deps += [ "//chrome/tools/build/win/syzygy:chrome_child_dll_syzygy" ]
-      }
     }
   }
 }
 
 # For compatibility with GYP. The linux_chromium_chromeos_rel_ng and
 # linux_chromium_chromeos_compile_rel_ng bots reference this target as
 # something to build, but all targets for those bots to compile are set
 # up differently.
 # TODO bug 601920: Remove reference to aura_builder on bot config and delete
 # this group.
@@ skipping 36 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }