Created placeholders for MallocHooks implementation and added define DART_USE_TCMALLOC to specifiy …

runtime/vm/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.
 
 import("../../build/executable_suffix.gni")
 import("../../build/prebuilt_dart_sdk.gni")
 import("gypi_contents.gni")
+import("../runtime_args.gni")
 
 config("libdart_vm_config") {
   if (defined(is_fuchsia) && is_fuchsia) {
     libs = [ "magenta" ]
   } else if (is_win) {
     libs = [
       "advapi32.lib",
       "shell32.lib",
       "dbghelp.lib",
     ]
@@ skipping 511 matching lines @@
       processed_gypis.vmservice_runtime_sources,
       "../lib",
     ],
     [
       "io",
       processed_gypis.bin_io_sources,
       "../bin",
     ],
   ]
 }