Moves BUILD.gn config from root to runtime.

runtime/third_party/jscre/BUILD.gn

 # Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 static_library("libjscre") {
-  configs += [ "../../..:dart_config", ]
+  configs += [ "../..:dart_config", ]
   defines = [
     "SUPPORT_UTF8",
     "SUPPORT_UCP",
     "NO_RECURSE",
   ]
   sources = [
     "ASCIICType.h",
     "config.h",
     "pcre.h",
     "pcre_internal.h",
     "ucpinternal.h",
     "pcre_compile.cpp",
     "pcre_exec.cpp",
     "pcre_tables.cpp",
     "pcre_ucp_searchfuncs.cpp",
     "pcre_xclass.cpp",
   ]
   include_dirs = [
     ".",
   ]
 }