supersize: Fix --tool-prefix autodetection

tools/binary_size/libsupersize/console.py

 # Copyright 2017 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.
 
 """An interactive console for looking analyzing .size files."""
 
 import argparse
 import atexit
 import code
 import contextlib
@@ skipping 241 matching lines @@
 
 def AddArguments(parser):
   parser.add_argument(
       'inputs', nargs='+',
       help='Input .size files to load. For a single file, it will be mapped to '
            'the variable "size_info". For multiple inputs, the names will be '
            'size_info1, size_info2, etc.')
   parser.add_argument('--query',
                       help='Execute the given snippet. '
                            'Example: Print(size_info)')
-  parser.add_argument('--tool-prefix', default='',
+  parser.add_argument('--tool-prefix',
                       help='Path prefix for objdump. Required only for '
                            'Disassemble().')
   parser.add_argument('--output-directory',
                       help='Path to the root build directory. Used only for '
                            'Disassemble().')
 
 
 def Run(args, parser):
   for path in args.inputs:
     if not path.endswith('.size'):
       parser.error('All inputs must end with ".size"')
 
   size_infos = [archive.LoadAndPostProcessSizeInfo(p) for p in args.inputs]
   lazy_paths = paths.LazyPaths(tool_prefix=args.tool_prefix,
                                output_directory=args.output_directory,
                                any_path_within_output_directory=args.inputs[0])
   session = _Session(size_infos, lazy_paths)
 
   if args.query:
     logging.info('Running query from command-line.')
     session.Eval(args.query)
   else:
     logging.info('Entering interactive console.')
     session.GoInteractive()