[Mac/GN] Add targets to run dump_syms and create the dSYM archive.

build/redirect_stdout.py

+# Copyright 2016 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 subprocess
+import sys
+
+# This script executes a command and redirects the stdout to a file. This is
+# equivalent to |command... > output_file|.
+#
+# Usage: python redirect_stdout.py output_file command...
+
+if __name__ == '__main__':
+  if len(sys.argv) < 2:
+    print >> sys.stderr, "Usage: %s output_file command..." % (sys.argv[0])
+    sys.exit(1)
+
+  with open(sys.argv[1], 'w') as fp:
+    sys.exit(subprocess.check_call(sys.argv[2:], stdout=fp))