[Mac/iOS/GN] Place a version in the command of toolchain tools implemented using scripts.

build/toolchain/mac/get_tool_mtime.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 os
+import sys
+
+# Usage: python get_tool_mtime.py path/to/file1.py path/to/file2.py
+#
+# Prints a GN scope with the variable name being the basename sans-extension
+# and the value being the file modification time. A variable is emitted for
+# each file argument on the command line.
+
+if __name__ == '__main__':
+  for f in sys.argv[1:]:
+    variable = os.path.splitext(os.path.basename(f))[0]
+    print '%s = %d' % (variable, os.path.getmtime(f))