python_arch: return "unknown" when file does not exist

build/linux/python_arch.sh

 #!/bin/sh
 # Copyright (c) 2011 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.
 
 # This figures out the architecture of the version of Python we are building
 # pyautolib against.
 #
 #  python_arch.sh /usr/lib/libpython2.5.so.1.0
 #  python_arch.sh /path/to/sysroot/usr/lib/libpython2.4.so.1.0
 #
 
 file_out=$(file --dereference "$1")
-if [ $? -ne 0 ]; then
+if [ $? -ne 0 ] || [ ! -e "$1" ] ; then

[Mark Mentovai, 2014/01/13 22:39:24]

A short form of your checkin comment would do a whole lot to explain what the -e
is about. Something like “the spec says that file should exit with status 0 when
a file does not exist.”

[vapier, 2014/01/13 22:45:19]

done

   echo unknown
   exit 0
 fi
 
 echo $file_out | grep -qs "ARM"
 if [ $? -eq 0 ]; then
   echo arm
   exit 0
 fi
 
 echo $file_out | grep -qs "MIPS"
 if [ $? -eq 0 ]; then
   echo mipsel
   exit 0
 fi
 
 echo $file_out | grep -qs "x86-64"
 if [ $? -eq 0 ]; then
   echo x64
   exit 0
 fi
 
 echo $file_out | grep -qs "Intel 80386"
 if [ $? -eq 0 ]; then
   echo ia32
   exit 0
 fi
 

[Mark Mentovai, 2014/01/13 22:39:24]

I’m inclined to do the -e check way down here, as it should be an uncommon case.

[vapier, 2014/01/13 22:45:19]

it's unlikely, but if the error message contains the string the rest of the code
is searching for, it could wrongly flag as an arch that it isn't

 exit 1