**/*.py: use /usr/bin/env to find python

pnacl/driver/pnacl-nmf.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # IMPORTANT NOTE: If you make local mods to this file, you must run:
 #   %  pnacl/build.sh driver
 # in order for them to take effect in the scons build.  This command
 # updates the copy in the toolchain/ tree.
 #
 
@@ skipping 197 matching lines @@
     # runnable_ld.so is going to ask for libgcc_s.so.1 even though it does
     # not show up in the pexe's NEEDED metadata, so it won't show up
     # in the NMF and on the App's webserver.
     #
     # For now, hack in libgcc_s.so.1.
     # http://code.google.com/p/nativeclient/issues/detail?id=2582
     needed.append('libgcc_s.so.1')
     GenerateDynamicNMF(exe_file, baseline_nmf, needed, output_file)
   DriverClose(output_file)
   return 0