gyp performance: Load detect_host_arch directly.

build/detect_host_arch.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """Outputs host CPU architecture in format recognized by gyp."""
 
 import platform
 import re
 import sys
 
 
 def main():
+  print DoMain([])
+  return 0
+
+def DoMain(_):
+  """Hook to be called from gyp without starting a separate python
+  interpreter."""
   host_arch = platform.machine()
 
   # Convert machine type to format recognized by gyp.
   if re.match(r'i.86', host_arch) or host_arch == 'i86pc':
     host_arch = 'ia32'
   elif host_arch in ['x86_64', 'amd64']:
     host_arch = 'x64'
   elif host_arch.startswith('arm'):
     host_arch = 'arm'
 
   # platform.machine is based on running kernel. It's possible to use 64-bit
   # kernel with 32-bit userland, e.g. to give linker slightly more memory.
   # Distinguish between different userland bitness by querying
   # the python binary.
   if host_arch == 'x64' and platform.architecture()[0] == '32bit':
     host_arch = 'ia32'
 
-  print host_arch
-  return 0
+  return host_arch
 
 if __name__ == '__main__':
   sys.exit(main())