[Swarming] Isolate valgrind runner.

build/has_valgrind.py

+#!/usr/bin/env python
+# Copyright 2016 the V8 project 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 os
+
+BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+VALGRIND_DIR = os.path.join(BASE_DIR, 'third_party', 'valgrind')
+LINUX32_DIR = os.path.join(VALGRIND_DIR, 'linux_x86')
+LINUX64_DIR = os.path.join(VALGRIND_DIR, 'linux_x64')
+
+
+def DoMain(_):
+  """Hook to be called from gyp without starting a separate python
+  interpreter."""
+  return int(os.path.exists(LINUX32_DIR) and os.path.exists(LINUX64_DIR))
+
+
+if __name__ == '__main__':
+  print DoMain([])