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

pnacl/unsupported/driver/pnacl-pexecheck.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2011 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:
 #   %  tools/llvm/utman.sh driver
 # in order for them to take effect in the scons build.  This command
 # updates the copy in the toolchain/ tree.
 #
 
 from driver_tools import *
 
 EXTRA_ENV = {
   # TODO(robertm): move this into the TC once this matures
   'PEXE_ALLOWED_UNDEFS': '${BASE_NACL}/tools/llvm/non_bitcode_symbols.txt',
 
   'RUN_PEXECHECK': '${LLVM_LD} --nacl-abi-check ' +
                    '--nacl-legal-undefs ${PEXE_ALLOWED_UNDEFS} ${inputs}',
 }
 env.update(EXTRA_ENV)
 
 def main(argv):
   """Check whether a pexe satifies our ABI rules"""
   return RunWithEnv('${RUN_PEXECHECK}', inputs=argv[0], errexit = False)
 
 if __name__ == "__main__":
   DriverMain(main)